Ebook Pathology of the maxillofacial bones A guide to diagnosis Part 1

(BQ) Part 1 book Pathology of the maxillofacial bones A guide to diagnosis presentation of content: Nonneoplastic diseases, cysts, epithelial odontogenic tumors, odontogenic tumors mesenchymal, odontogenic tumors mixed epithelial and mesenchymal, odontogenic tumors malignant.

Pathology of the

Maxillofacial Bones

123

A Guide to Diagnosis Pieter Slootweg

Pathology of the Maxillofacial Bones

Pieter Slootweg

Pathology of the

Maxillofacial Bones

A Guide to Diagnosis

ISBN 978-3-319-16960-6 ISBN 978-3-319-16961-3 (eBook)

DOI 10.1007/978-3-319-16961-3

Library of Congress Control Number: 2015941516

Springer Cham Heidelberg New York Dordrecht London

© Springer International Publishing Switzerland 2015

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The maxillofacial skeleton, which comprises the jaws and the bony walls of the sinonasal cavities, is the site of a huge variety of lesions of a widely diver-gent nature Some of them have no counterparts elsewhere in the skeleton because the tissues from which they arise are confi ned to the maxillofacial bones Prime examples of these are the odontogenic cysts and tumors Other lesions are not confi ned to the maxillofacial skeleton but may pose differen-tial diagnostic problems that are unique for this area; an illustrative example

of this category forms craniofacial fi brous dysplasia that has a much wider differential diagnosis than shown by the same lesion at other body sites Furthermore, maxillofacial bone pathology still heavily relies on plain his-tomorphology Immunohistochemistry and molecular pathology only play a rather modest role, and, quite often, careful examination of a hematoxylin- and eosin-stained slide is the only way to obtain the result that is needed to provide the clinician with the correct diagnosis upon which treatment should

be based

Therefore, the entities discussed in this book are lavishly illustrated in an attempt to show both the full spectrum of morphological varieties and the features that are decisive in making decisions among diseases sharing com-mon histomorphological features

Text and illustrations are based on specimens collected over a period of more than 40 years, and it is my privilege to acknowledge the courtesy of all colleagues who have contributed by either sending cases for consultation or otherwise by joining discussions on diagnostic issues during slide seminars

or at other occasions Hopefully, the book will serve as a reliable guide for those practicing the pathology of the bones that are the building blocks of the maxillofacial skeleton

Nijmegen , The Netherlands Pieter Slootweg

1 Non-neoplastic Diseases 1

1.1 Introduction 1

1.2 Exostosis 1

1.3 Osteoma 1

1.4 Osteomyelitis 4

1.5 Odontomaxillary Dysplasia 8

1.6 Bullough’s Lesion 9

References 10

2 Cysts 11

2.1 Introduction 11

2.2 Odontogenic Cysts – Infl ammatory 11

2.2.1 Radicular Cyst 11

2.2.2 Paradental Cyst 13

2.3 Odontogenic Cysts – Developmental 16

2.3.1 Dentigerous Cyst 16

2.3.2 Lateral Periodontal Cyst 20

2.3.3 Glandular Odontogenic Cyst 21

2.3.4 Keratocystic Odontogenic Tumor 23

2.4 Non-odontogenic Cysts 27

2.4.1 Surgical Ciliated Cyst 28

2.5 Pseudocysts 29

2.5.1 Solitary Bone Cyst 29

2.5.2 Focal Bone Marrow Defect 30

References 31

3 Epithelial Odontogenic Tumors 33

3.1 Introduction 33

3.2 Ameloblastoma 33

3.3 Calcifying Epithelial Odontogenic Tumor 47

3.4 Adenomatoid Odontogenic Tumor 51

3.5 Squamous Odontogenic Tumor 57

References 58

4 Odontogenic Tumors: Mesenchymal 61

4.1 Introduction 61

4.2 Odontogenic Myxoma 61

4.3 Odontogenic Fibroma 63

4.4 Cementoblastoma 68

References 75

5 Odontogenic Tumors: Mixed Epithelial and Mesenchymal 77

5.1 Introduction 77

5.2 Calcifying Cystic Odontogenic Tumor 77

5.3 Ameloblastic Fibroma 81

5.4 Ameloblastic Fibro-Odontoma 85

5.5 Odontoma – Complex Type 88

5.6 Odontoma – Compound Type 90

5.7 Odonto-Ameloblastoma 91

References 96

6 Odontogenic Tumors: Malignant 99

6.1 Introduction 99

6.2 Malignant Ameloblastoma 99

6.3 Ameloblastic Carcinoma 99

6.4 Primary Intraosseous Carcinoma 99

6.5 Clear Cell Odontogenic Carcinoma 106

6.6 Malignant Epithelial Odontogenic Ghost Cell Tumor 109

6.7 Sclerosing Odontogenic Carcinoma 111

6.8 Odontogenic Sarcomas 115

References 121

7 Fibro-Osseous Lesions 123

7.1 Introduction 123

7.2 Fibrous Dysplasia 123

7.3 Ossifying Fibroma 132

7.4 Osseous Dysplasia 148

References 155

8 Giant Cell Lesions 157

8.1 Introduction 157

8.2 Central Giant Cell Granuloma 157

8.3 Cherubism 164

8.4 Aneurysmal Bone Cyst 167

References 170

9 Bone Tumors 171

9.1 Introduction 171

9.2 Osteoblastoma 171

9.3 Osteosarcoma 178

References 195

Contents

10 Tumors of Cartilage 197

10.1 Introduction 197

10.2 Chondromyxoid Fibroma 197

10.3 Chondroblastoma 203

10.4 Chondrosarcoma 206

10.5 Mesenchymal Chondrosarcoma 211

References 216

11 Other Lesions Involving the Maxillofacial Skeleton 217

11.1 Introduction 217

11.2 Desmoplastic Fibroma 217

11.3 Non-ossifying Fibroma 220

11.4 Melanotic Neuroectodermal Tumor of Infancy 221

11.5 Myoepithelial Tumors 222

11.6 Chordoma 224

11.7 Epitheloid Hemangioendothelioma 229

References 232

12 Diseases of the Temporomandibular Joint 235

12.1 Introduction 235

12.2 Reactive Changes 235

12.3 Osteoarthritis 235

12.4 Infl ammatory Disorders 237

12.5 Neoplasms 239

12.6 Synovial Chondromatosis 239

12.7 Condylar Hyperplasia 240

References 248

Index 249

© Springer International Publishing Switzerland 2015

P Slootweg, Pathology of the Maxillofacial Bones: A Guide to Diagnosis,

DOI 10.1007/978-3-319-16961-3_1

Non-neoplastic Diseases

1.1 Introduction

The jaws and sinonasal walls may show reactive

bony outgrowths that may cause functional

prob-lems Moreover, infl ammatory processes leading to

bone loss may be of clinical signifi cance This

Chapter discusses their specifi c histological features

as well as differential diagnostic considerations that

allow distinction from genuine neoplasms

1.2 Exostosis

The jaws may show bony outgrowths at their

sur-face These exostoses , also called tori occur at

the tooth-bearing part, the so-called alveolar

pro-cess that houses the roots of the teeth in which

case they mostly occur at the outer side that lies

opposite to the mucosal surface of lip or cheek

Other involved sites are the lingual surface of the

mandible or the midline of the palate (Fig 1.1 )

Histologically, they are composed of dense

lamellar bone that is continuous with the

under-lying cortical bone of the jaw (Fig 1.2 ) However,

they are rarely submitted for histological analysis

as usually, they can be left untouched unless

interfering with dental prosthetic treatment So

they are more important for the dentist than for

the surgical pathologist However, in case of jaw

specimens only showing compact lamellar bone

on histological examination, one should consider

this diagnostic possibility but only in case of

corresponding clinical information as there are

no histological features that allow distinction between tori and normal compact lamellar bone from the peripheral jaw cortical layer

1.3 Osteoma

Osteomas are outgrowths that mainly consist of compact lamellar bone In the maxillofacial skeleton, they most commonly occur in the frontal and ethmoid sinus; less often, the maxil-lary antrum and the sphenoid sinus are involved [ 1 ] They may also occur in the jaw bones either sporadic or as manifestation of Gardner’s syndrome [ 2 ]

1

Fig 1.1 Lingual view of mandible showing torus senting itself as a bony thickening of the lingual alveolar plate

Osteomas usually show a peripheral thick

layer of compact lamellar bone that is covered

by a thin rim of respiratory mucosa (Fig 1.3 )

When moving away from the surface, this

compact bone gradually transforms into coarse

or slender bone trabeculae within a fatty or

fi brous background that merge with the

adja-cent pre-existent cancellous bone Sometimes,

such a compact peripheral part is absent,

the less dense trabecular component lying

immediately underneath the covering tory mucosa (Fig 1.4 ) Occasionally, also thin trabeculae of woven bone lined with prominent osteoblasts are present at the interface of the osteoma and the adjacent cancellous bone (Fig 1.5 )

If located within the jawbone, osteomas pose a differential diagnostic problem as they need to be distinguished from other bone containing lesions

of the jaws, such as central ossifying fi broma,

Fig 1.2 Torus

histologi-cally showing thickening of

alveolar socket composed of

compact lamellar bone

Fig 1.3 Osteoma covered

with thin layer of respiratory

mucosa Peripheral part is

compact; central part more

trabecular with loose

fi brovascular stroma

osseous dysplasia, osteoblastoma,

cementoblas-toma, and complex odontoma [ 3 ] Most of these

lesions however show a fi brocellular soft tissue

component that is different from the fi brofatty

soft tissue present in osteomas Moreover, other

hard tissue components than only lamellar bone

are found in them The only real problem may be

encountered when dealing with central osteoma

and localized chronic sclerosing osteomyelitis if they occur in the mandible as both lesions display

a fi brotic marrow and mainly lamellar bone In those cases, clinical data will be decisive, osteo-mas usually being an incidental fi nding on radio-graphs taken for some other reasons, e.g during routine dental diagnostics and osteomyelitis causing clinical symptoms

Fig 1.4 Peripheral part of

osteoma composed of

slender trabeculae In this

case, the compact peripheral

part as usually seen is

1.4 Osteomyelitis

Osteomyelitis is characterized by infl ammation

of the bone marrow accompanied with bone

necrosis and sclerosis The condition mainly

involves the mandible, probably due to its

com-pact nature in comparison with the more loosely

textured maxilla Although it may be seen at any

age, children are rarely affected

Osteomyelitis may occur through extension of

infection of the dental pulp or as a complication

after tooth extraction After irradiation of the

head and neck area as done for head and neck

cancer, the subsequent decreased vascularisation

of the jaw bone may cause increased

vulnerabil-ity to infection An infl ammatory reaction in

the poorly vascularised bone may develop; a

condition known as osteoradionecrosis Also,

bisphosphonates, a class of drugs that prevent the

loss of bone mass and therefore are used to treat

osteoporosis and related disorders such as Paget’s

disease, bone metastasis, multiple myeloma, and

other conditions that feature bone fragility, have

been associated with the development of necrosis

and subsequent infection of the jaw bone [ 4 ]

Five different types of osteomyelitis can be

discerned: acute suppurative osteomyelitis,

chronic suppurative osteomyelitis, chronic focal

sclerosing osteomyelitis, chronic diffuse ing osteomyelitis, and proliferative periostitis Radiographs show an ill-defi ned mixed radiodense and radiolucent lesion In case of acute osteomy-elitis, pain and fever occur and intraoral examination may reveal sinuses or dead bone sequestered through mucosal defects In chronic osteomyelitis, slight discomfort may be the sole symptom

Histologically, acute suppurative

osteomyeli-ti s shows bone marrow caviosteomyeli-ties infi ltrated with

neutrophils The bony trabeculae are necrotic as can be inferred from empty osteocyte lacunae and peripheral resorption lacunae (Fig 1.6 ) Usually, this form of osteomyelitis evolves into chronic suppurative osteomyelitis which also may arise de novo Besides bone sequesters sur-rounded by numerous neutrophilic granulocytes also granulation tissue is present Sinuses are formed partly lined by squamous epithelium from the oral mucosa (Fig 1.7 ) In less severe cases, fi brosis and development of a chronic infl ammatory infi ltrate may also be seen When the infl ammation is mild, the jaw bone responds

by bone formation This form of osteomyelitis is known as chronic sclerosing which may be focal

as well as diffuse Dense sclerotic bone masses are seen together with a bone marrow exhibiting

Fig 1.6 Acute osteomyelitis is characterized by bone

fragments with empty lacunae and an irregular outline

due to osteoclastic resorption Marrow cavities and

surrounding soft tissues contain abundant neutrophilic granulocytes

edema and small foci of lymphocytes and plasma

cells (Fig 1.8 ) When the infl ammation mainly

involves the periosteum, the disease is called

proliferative periostitis, or called periostitis ossifi

-cans Histologically, one sees bony trabeculae

that lie in a linear parallel pattern, either parallel

to the cortical surface or perpendicular to it The

intervening stroma is composed of fi brous

con-nective tissue sparsely infi ltrated with

lympho-cytes and plasma cells (Figs 1.9 and 1.10 ) The

parallel pattern of the newly formed bone

is refl ected in the radiographs in which also a

multilayering is shown (Fig 1.11 )

In osteoradionecrosis, necrotic bone may also lie in fi brotic areas without any infl ammatory infi ltrate (Fig 1.12 ) Furthermore, the patient’s history will be helpful in distinguishing osteoradionecrosis with subsequent infl amma-tion from osteomyelitis as a sequel of dental problems In a similar way, the patient’s medical history will reveal the use of biphosphonates as

an explanation for the histologic fi ndings

Acute suppurative osteomyelitis rarely causes differential diagnostic problems The only issue is not to confuse epithelial-lined sinuses with invading squamous cell carcinoma This mistake especially

Fig 1.7 Mucosal

perfora-tion of dead bone may lead

to formation of sinuses lined

by squamous epithelium that

may be mistaken for

squamous cell carcinoma

invading bone

Fig 1.8 Chronic

osteomy-elitis shows dense sclerotic

lamellar bone surrounded

with edematous bone marrow

containing small foci of

lymphocytes and plasma

cells

1.4 Osteomyelitis

may occur in cases of osteoradionecrosis after diation for cancer treatment when material from the jaw is submitted to rule out or confi rm recurrent squamous cell carcinoma

Both focal as well as diffuse chronic ing osteomyelitis must be distinguished from other bone lesions, especially the fi bro-osseous

Fig 1.9 In proliferative periostitis, the bony trabeculae

lie parallel to each other, in this case perpendicular to the

surface but an orientation parallel to the surface also may

occur

Fig 1.10 Higher magnifi

ca-tion of Fig 1.9 to show the

border between cortical bone

(vertical) and newly formed

reactive bone (horizontal)

Fig 1.11 The parallel arrangement of newly formed bone in case of periostitis is also refl ected in the radiologi- cal appearance showing a multiplication of the cortical border as can be seen when comparing the left and the right ascending mandibular ramus

ones Edematous marrow with sprinkled

lympho-cytes and dense sclerotic bone allow its

distinc-tion from the fi bro-osseous lesions with their

cellular fi broblastic stroma Paget’s disease enters

the differential diagnosis as it may mimic chronic

sclerosing osteomyelitis radiologically but its

histology differs profoundly; bone marrow containing dilated thin-walled blood vessels, numerous osteoclasts and prominent reversal lines in the bone causing the proverbial mosaic pattern are typical for Paget’s disease and absent

in chronic sclerotic osteomyelitis (Fig 1.13 )

Fig 1.12 Osteoradionecrosis can be distinguished from

osteomyelitis by the absence of any infl ammatory

infi ltrate, dead bone lying in dense sclerotic fi brous

tissue In general however, osteoradionecrosis will show

concomitant infl ammation; in that case both diseases cannot be distinguished histologically, the patient’s history being needed for making the correct diagnosis

Fig 1.13 Paget’s disease of

the bone characterized by

irregular bony trabeculae

with prominent reversal

lines, vascular bone marrow

and abundant osteoclasts

1.4 Osteomyelitis

Fig 1.14 Cortical bone

showing expansion and

remodeling due to an

intraosseous benign neoplasm

showing expansive growth

This picture may also be seen

in proliferative periostitis but

the clinical and radiological

symptoms allow the

distinction between both

diseases

The parallel arrangement of bony trabeculae

that characterizes proliferative periostitis may

also occur when a benign intraosseous jaw

tumor causes expansion and remodeling of the

overlying cortical bone (Fig 1.14 ) This may

cause a diagnostic problem when the biopsy

from such a lesion is taken too superfi cial, thus

containing only the reactive border and not the

lesion itself In such cases, one has to decide

whether the tissue submitted for histology

should be diagnosed as compatible with a

diag-nosis of proliferative periostitis or whether the

sample does not contain representative material

Knowledge of the clinical and radiological data

is mandatory to make the proper diagnosis in

such a situation and when these data are

indica-tive of tumor, one should ask for a new and

more representative biopsy

Treatment of osteomyelitis consists of otics and surgery Unless the sequestra are removed, the disease will not heal Especially in case of chronic sclerotic osteomyelitis, the dis-ease may respond poorly to treatment and run a protracted course

antibi-1.5 Odontomaxillary Dysplasia

Odontomaxillary dysplasia is a noninherited, sporadic, developmental, condition that presents early in life and is characterized by asymptom-atic unilateral enlargement of the maxilla Radiographically, the bone of the affected region exhibits a localized, ill-defi ned increased bone density owing to coarse, irregular trabeculae with

a variable vertical orientation Histopathologically,

the lesion is composed of thickened, irregularly

shaped trabeculae of immature woven bone with

bone marrow spaces changed into loose

paucicel-lular fi brous tissue (Fig 1.15 ) [ 5 ] Differential

diagnosis includes fi brous dysplasia that has a

more fi brocellular soft tissue component and

chronic sclerosing osteomyelitis in which the

bone is not woven but lamellar Moreover, this

latter lesion involves mainly the mandible

whereas the odontomaxillary dysplasia is

con-fi ned to the maxilla

1.6 Bullough’s Lesion

Bullough lesion is a lesion at the surface of the temporal bone that presents as a retroauricular soft tissue mass with calcifi c densities, confi ned to the soft tissues on the outer table of the skull without intraosseous involvement The lesion is character-ized histologically by rounded and ovoid zones of ossifi cation within a bland fi brous stroma and so is different from fi brous dysplasia both by its loca-tion and histology (Figs 1.16 and 1.17 )

Fig 1.15 Odontomaxillary

dysplasia showing disturbed

bone architecture and a

fi broblastic background See

text for differential

diagnos-tic considerations versus

fi bro- osseous jaw lesions

Fig 1.16 Bullough’s lesion

consisting of osseous

spheroids in a fi brous

background

1.6 Bullough’s Lesion

Only a few cases of this entity have been reported

until now [ 6 ] If one is aware of its presence,

diag-nosis is not diffi cult due to its typical location:

outside the bone in the retroauricular soft tissues

When this information is lacking, the lesion cannot

be distinguished from other lesions that combine

bone formation and fi brosis

References

1 Samy LL, Mostafa H Osteomata of the nose and

para-nasal sinuses with a report of twenty-one cases J

Laryngol Otol 1971;85(5):449–69

2 Williams SC, Peller PJ Gardner’s syndrome Case report and discussion of the manifestations of the dis- order Clin Nucl Med 1994;19(8):668–70

3 Kaplan I, Nicolaou Z, Hatuel D, Calderon S Solitary central osteoma of the jaws: a diagnostic dilemma Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106(3):e22–9

4 Pazianas M Osteonecrosis of the jaw and the role of macrophages J Natl Cancer Inst 2011;103(3):232–40

5 Whitt JC, Rokos JW, Dunlap CL, Barker BF Segmental odontomaxillary dysplasia: report of a series of 5 cases with long-term follow-up Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112(2):e29–47

6 Sia SF, Davidson AS, Soper JR, Gerarchi P, Bonar

SF Protuberant fi bro-osseous lesion of the temporal bone: “Bullough lesion” Am J Surg Pathol 2010; 34(8):1217–23

Fig 1.17 At higher

magnifi cation, the bony

particles in Bullough’s lesion

are surrounded by a

peripheral fi brocellular rim

and radiating fi bers

© Springer International Publishing Switzerland 2015

P Slootweg, Pathology of the Maxillofacial Bones: A Guide to Diagnosis,

DOI 10.1007/978-3-319-16961-3_2

Cysts

2.1 Introduction

Cysts of the jaws are classifi ed in distinct

catego-ries depending on histogenesis and etiology

Those that arise from odontogenic epithelium are

called odontogenic, those that have their source

in other epithelial structures are known as non-

odontogenic Within the odontogenic cysts and

based on etiology, one discerns between infl

am-matory and developmental [ 1] By defi nition,

cysts are lined by epithelium but there are also

cavities in the jaws that lack such an epithelial

investment; they are included in this Chapter as

well for differential diagnostic considerations

2.2 Odontogenic

Cysts – Infl ammatory

2.2.1 Radicular Cyst

Radicular cysts are cystic lesions located at the

root tips of teeth (Figs 2.1 and 2.2 ) [ 2 ] and they

arise from the rests of Malassez, remnants of

dental epithelium involved in root formation that

lie in the fi brous tissue that connects the tooth

with its jaw socket, the so-called periodontal

lig-ament When triggered by infl ammation, usually

due to tooth decay, these epithelial nests increase

in size whereafter they turn into a cyst due to

sub-sequent liquefaction necrosis of the central part

(Figs 2.3 and 2.4) It is the most frequently encountered odontogenic cyst [ 3 4 ]

Histologically, these cysts are lined by ratinizing stratifi ed squamous epithelium that may show elongated rete processes that may form arches (Fig 2.5 ) or are thin and atrophic (Fig 2.6 ) Also, pronounced intercellular edema may be shown (Fig 2.7 ) In many cysts, choles-

2

Fig 2.1 Radiograph showing radicular cyst A large radiolucent lesion surrounds the apices of 2 anterior inci- sor teeth that have their roots fi lled to treat pulpal infl am- mation Before treatment, this pulpal disease has spread through the apical root foramen into the adjacent jaw bone with as outcome cyst formation resulting in local loss of bone

terol clefts with adjacent giant cells occur

Within the cyst epithelium, hyaline bodies

(Rushton bodies) of various size and shape may

be present (Fig 2.8 ), the specifi c nature of which

remains unclear [ 5] Occasionally, the lining

squamous cells are admixed with mucous cells

or ciliated cells (Fig 2.9 ) In maxillary cysts,

this fi nding could be explained by the vicinity of

the lesion to respiratory mucoa lining the

maxil-lary sinus or nasal cavity but as these cells also

occur in the lining of cysts in the mandible, it

represents genuine aberrant differentiation of

odontogenic epithelium Sometimes, the

histo-logic pattern of the radicular cyst is complicated

by extensive intramural proliferation of

squa-mous epithelial nests of varying size, thus

mim-icking a squamous odontogenic tumor (Fig 2.10 )

[ 6 ] A similar histology may be shown by other

jaw cysts, in particular when there are extensive

infl ammatory changes that obscure the more

specifi c histological details of these latter ones

When differentiating between a genuine

radicu-lar cyst and one of these other jaw cysts, one should realize that radicular cysts usually are small and located at the root tip of a decayed tooth If cysts histologically resembling a radic-ular cyst are not in the periapical tooth area, not related to a decayed tooth and have a big size thus involving large areas of the mandible, one should be suspicious that one is dealing with a dentigerous cyst, an odontogenic keratocyst, or a unicystic ameloblastoma in which the specifi c diagnostic features have disappeared due to sec-ondary infl ammatory changes In those cases, it

is the best approach to make a note that possibly, the submitted specimen is not representative for the lesion Another item of diagnostic confusion may arise when the Rushton bodies are mistaken for ghost cells, a feature in a lot of odontogenic lesions that will be dealt with later on in more detail

When a radicular cyst is retained in the jaws after removal of the associated tooth, the lesion is

called residual cyst

Fig 2.2 Bisected molar

tooth with attached radicular

cyst Occasionally, a

radicular cyst remains

attached to the roots during

tooth extraction (Reproduced

from Slootweg [ 2 ])

2.2.2 Paradental Cyst

The paradental cyst is a cystic lesion located at

the lateral side of the tooth at the border

between tooth crown and root surface The cyst

is secondary to an infl ammatory process in the

adjacent periodontal tissues that induces liferation of neighboring odontogenic epithe-lial rests, similar to the pathogenesis of the radicular cyst [ 7 , 8 ] and its histological fea-tures are the same Only the site is different, radicular cysts lying at the root tip and the paradental cysts located at the root surface close to the tooth crown Moreover, radicular cysts are the results of tooth decay and para-dental cysts are associated with infl ammation

pro-of the spro-oft tissues that surround the neck pro-of the tooth, the tooth itself being without any pathol-ogy When keeping this in mind, the distinction between radicular and paradental cyst is rela-tively easy provided the relevant clinical data are provided

Fig 2.3 Low power view showing infl ammatory infi

l-trate at the root tip of a decayed tooth Radicular cyst

development may be a sequel of this condition due to

reactive proliferation of odontogenic epithelial remnants

located in the periodontal ligament

Fig 2.4 In areas of infl ammation at the root apex, togenic epithelial remnants increase in size Central lique- faction in these epithelial clusters transforms them into a cyst lined with epithelium, usually of the squamous type 2.2 Odontogenic Cysts – Infl ammatory

Fig 2.5 Radicular cysts are

lined by non-keratinizing

squamous epithelium that

may show elongated rete

ridges sometimes forming

roman arches

Fig 2.6 Detail of the lining

of a radicular cyst, in this case

composed of a thin layer of

squamous epithelium

Fig 2.7 In case of

infl ammation, the epithelial

lining may show spongiotic

changes that should not be

confused with the stellate

reticulum present in

ameloblastoma

Fig 2.8 Intraepithelial

acellular deposits known as

Rushton bodies are a

common feature in a variety

of odontogenic cysts They

should not be confused with

ghost cells

2.2 Odontogenic Cysts – Infl ammatory

2.3 Odontogenic

Cysts – Developmental

2.3.1 Dentigerous Cyst

The dentigerous (follicular) cyst is a very

com-mon lesion Its radiologic and gross appearance

is highly characteristic, a cyst lumen in which the

tooth crown protrudes and a cyst wall that is attached to this tooth at the junction between crown and root (Figs 2.11 and 2.12 ) [ 9 ] Probably, this cyst arises from fl uid accumulation between the tooth’s enamel surface and the rem-nants of the epithelial enamel organ that invests the tooth crown as long as the tooth has not erupted in the oral cavity

Fig 2.9 Mucous cells and

ciliated cells may be present

in the lining of radicular

cysts This is an incidental

fi nding without any

diagnostic signifi cance In

this picture, ciliated cells are

shown

Fig 2.10 Large intramural

nests of odontogenic

epithelium can be found in

radicular cysts This may

mimic squamous

odonto-genic tumor

Microscopical examination shows a cyst

wall that is connected to the tooth at the

cement- enamel junction (Fig 2.13 ) and

usu-ally with a thin epithelial lining that may be

only two to three cells thick (Fig 2.14 ) In case

of infl ammation, the epithelium becomes

thicker and may resemble that of a radicular

cyst Also, mucous producing cells as well as

ciliated cells may be observed (Fig 2.15 ) The

connective tissue component of the cyst wall

may be fi brous or fi bromyxomatous and may

also contain varying amounts of epithelial nests representing remnants of the dental lam-ina and should not be mistaken for some type

of odontogenic neoplasm (Fig 2.16 ) Occasionally, the cyst wall may show aggre-gates of tiny amorphous calcifi cations, usually associated with odontogenic epithelial nests (Figs 2.17 and 2.18 ) This close association between odontogenic epithelium and calcifi ed deposits is however not unique for dentigerous cysts but is a general feature of odontogenic epithelial remnants

These fi bromyxomatous areas in the tive tissue wall of a dentigerous cyst may resem-ble odontogenic myxoma and the presence of odontogenic epithelial rests may lead to the erro-neous diagnosis of one or another type of epithe-lial odontogenic tumor [ 10 ] However, identifi cation of the epithelial cyst lining will rule out these alternatives

The eruption cyst is a specifi c type of

dentig-erous cyst located in the gingival soft tissues overlying the crown of an erupting tooth Mostly, these cysts are short-lived, rupturing with pro-gressive eruption of the associated tooth They are lined by squamous epithelium that is thick-ened due to infl ammatory changes in the underly-ing connective tissue and thus similar to the lining of a radicular cyst

Removal of the cyst wall and the involved tooth will yield a permanent cure

Fig 2.11 Radiograph of

dentigerous cyst The crown

of the right mandibular 3rd

molar tooth is surrounded by

a radiolucent lesion partly

extending into the

mandibu-lar ramus

Fig 2.12 Gross view of dentigerous cyst The cyst wall

is attached to the neck of the involved tooth which is a

typical feature for this odontogenic developmental cyst

(Reproduced from Flucke and Slootweg [ 9 ])

2.3 Odontogenic Cysts – Developmental

Fig 2.13 Low power view

of a dentigerous cyst The

attachment of the cyst wall to

the neck of a tooth is the

diagnostic hallmark of this

lesion but can only be

visualized when tooth and

cyst wall are processed for

histology as a single block

Fig 2.14 A thin

multilay-ered cuboidal epithelium is

the most simple lining of a

dentigerous cyst

Fig 2.15 Mucous cells and

ciliated cells may form part

of the lining of dentigerous

cysts In this Figure, mucous

cells are shown

Fig 2.16 Wall of

dentiger-ous cyst showing a large nest

of odontogenic epithelium

composed of ameloblastoma-

like cells and ghost cells

This should be considered a

tiny hamartomatous lesion

without clinical signifi cance

Similar aggregates can be

found in hyperplastic dental

follicles

2.3 Odontogenic Cysts – Developmental

2.3.2 Lateral Periodontal Cyst

Lateral periodontal cysts are rare lesions, derived

from odontogenic epithelial remnants, and

occurring on the lateral aspect or between the

roots of vital teeth, this latter feature similar as

for the paradental cyst [ 11] Usually they are

asymptomatic and fortuitous fi ndings on graphs, where they present as well- demarcated radiolucencies on the lateral surface of a tooth root (Fig 2.19 )

These cysts are lined by thin, ing squamous or cuboidal epithelium with focal, plaque-like thickenings consisting of

Fig 2.17 Large areas of

calcifi cation in the wall of a

dentigerous cyst

Fig 2.18 Higher magnifi

ca-tion of Figure 2.17 showing

the close relationship

between epithelium and

calcifi ed material

clear cells that may contain glycogen (Figs 2.20 and 2.21 ) [ 12 ]

The botryoid odontogenic cyst represents a

multilocular form of the lateral periodontal cyst [ 13] Histologically, the same epithelial lining including presence of plaques is observed

2.3.3 Glandular Odontogenic Cyst

The glandular odontogenic cyst, also called sialo -

odontogenic cyst is a cystic lesion characterized

by an epithelial lining with cuboidal or columnar cells both at the surface and lining crypts or cyst- like spaces within the thickness of the epithelium [ 1 3 ] The lesion is rare

This cyst most commonly affects the body of the mandible, particularly the anterior part, and the most prominent symptom is painless swelling

Histologically, the lining epithelium is partly non-keratinizing squamous with focal thicken-ings similar to the plaques in the lateral periodon-tal cyst and the botryoid odontogenic cyst There may be a surface layer of eosinophilic cuboidal

or columnar cells that may be ciliated and form papillary projections Some superfi cial cells may

Fig 2.19 Radiograph of lateral periodontal cyst showing

a small radiolucent lesion in the interdental bony septum

Fig 2.20 Lateral

periodon-tal cysts have a lining

composed of non-diagnostic

thin, non-keratinizing

squamous or cuboidal

epithelium Local

thicken-ings, the so-called plaques

are the defi ning diagnostic

feature

2.3 Odontogenic Cysts – Developmental

assume an apocrine appearance and mucous-

producing cells may be present The epithelium

shows focally increased thickness in which

glan-dular spaces are formed Moreover, the epithelial

cells may lie in spherical structures with a

whorled appearance (Figs 2.22 and 2.23 )

This cyst has to be distinguished from other

jaw cysts that occasionally contain mucous cells

and ciliated cuboidal cells which may form part

of the lining of radicular cysts and dentigerous

cysts as well However, these other cysts lack the

epithelial whorls, apocrine differentiation and intraepithelial glandular spaces, features as described above Another important differential diagnostic consideration is mucoepidermoid car-cinoma that also may contain mucous cells and nonkeratinizing squamous epithelium [ 14 – 16 ] However, epithelial plaques consisting of clear cells are not a feature of this latter lesion In fact, clear cells in mucoepidermoid carcinoma tend to

be more haphazardly distributed throughout the tumor, are larger in size and do not show a close

Fig 2.21 Higher magnifi

ca-tion of the plaques,

diagnostic for both the lateral

periodontal cyst as well as

the botryoid odontogenic

cyst

Fig 2.22 Cyst lining of the

glandular odontogenic cyst

The epithelial shows focal

thickenings in which the

cells may show a whirling

pattern; moreover glandular

lumina are present

association with the luminal surface of the lesion

Recognition of this lesion and its differentiation

from other cystic jaw lesions is important as

recurrences in up to 30 % of the cases may be

observed after conservative treatment [ 17 ]

2.3.4 Keratocystic

Odontogenic Tumor

Originally knows as odontogenic keratocyst , the

keratocystic odontogenic tumor is a cystic lesion

with a distinctive epithelial lining that should not

be misinterpreted by the histopathologist as this

disease shows a neoplastic nature In view of this

behavior, the name of the lesion has been changed

from odontogenic keratocyst into keratocystic

odontogenic tumor in the current WHO classifi

-cation of odontogenic tumors [ 18 ], but this

desig-nation is not yet universally accepted

Keratocystic odontogenic tumors are rather

common lesions [ 19 – 21 ] that are more frequently

seen in the mandible than in the maxilla and

involvement of the gingival soft tissues

(periph-eral odontogenic keratocyst) has also been

reported [ 22 ] They may also occur in the context

of the nevoid basal cell carcinoma (Gorlin- Goltz’s) syndrome and in patients with Marfan syndrome [ 23 – 25 ]

Keratocystic odontogenic tumors are tomatic unless concomitant infl ammation causes pain and swelling; they are more commonly located in the posterior mandible and are some-times associated with impacted teeth Radiographs may reveal extensive uni- or multi-locular radiolucent lesions that occupy the major part of the jaw without appreciable cortical expansion (Fig 2.24 )

The keratocystic odontogenic tumor shows a thin connective tissue wall lined by stratifi ed squamous epithelium with a well-defi ned basal layer of palisading columnar or cuboidal cells and with a superfi cial corrugated layer of para-keratin (Fig 2.25 ) Mitotic fi gures can be identi-

fi ed in parabasal and midspinous areas [ 26 ] and Rushton bodies, similar to those seen in radicular cysts, may also be present (Fig 2.26 ) The underlying cyst wall may contain tiny daughter cysts and solid epithelial nests (Fig 2.27 ); both are more common in cysts associated with the

Fig 2.23 At higher

magnifi cation, the superfi cial

cells of the glandular

odontogenic cyst may show

apocrine differentiation Also

columnar epithelium with

cilia can be encountered

2.3 Odontogenic Cysts – Developmental

Fig 2.24 Radiology of

keratocystic odontogenic

tumor A radiolucent area is

visible around the impacted

left lower canine This

radiological picture is

suggestive for a dentigerous

cyst but histological

examination showed the

appearance of a keratocystic

odontogenic tumor

Fig 2.25 Basal palisading

and a superfi cial corrugating

surface showing

parakerati-nization are the defi ning

features of a keratocystic

odontogenic tumor

Fig 2.26 Rushton bodies

are most often seen in

radicular cysts but

keratocys-tic odontogenic tumor may

show them as well as shown

in this case In the area

shown, the typical features of

a keratocystic odontogenic

tumor have disappeared due

to secondary reactive

changes Elsewhere in this

specimen, areas as shown in

Fig 2.25 were present

allowing the correct

diagnosis

nevoid basal cell carcinoma syndrome [ 27 ]

Furthermore, the small odontogenic epithelial

nests similar to those encountered in a lot of other

intraosseous jaw lesions and considered to be a

fortuitous fi nding without diagnostic relevance

may occur (Figs 2.28 and 2.29 )

Additional histological features sometimes observed in keratocystic odontogenic tumor are mucous cells, melanin producing cells, dentinoid and intramural cartilage [ 28 – 30 ] Also, ciliated cells may be seen but in maxillary cases, they probably come from a

Fig 2.27 Keratocystic

odontogenic tumor wall

showing extensive intramural

presence of daughter cysts

and solid epithelial nests

Fig 2.28 As in other jaw cysts, the fi brous wall of a

keratocystic odontogenic tumor may contain a lot of

odontogenic epithelial nests These are an incidental fi

nd-ing without any clinical signifi cance and should not be

considered as evidence for some specifi c odontogenic neoplasm At the left side, a small fragment of the cyst lining is shown

2.3 Odontogenic Cysts – Developmental

Fig 2.29 Occasionally, the

intramural epithelial nests

may be rather numerous

Fig 2.30 Jaw cysts showing

hyperorthokeratosis should

not be mistaken for a

keratocystic odontogenic

tumor Moreover, there is no

basal palisading present

These lesions should be

diagnosed as

orthokera-tinized odontogenic cyst

communication with the maxillary sinus [ 31 ]

In addition, the cyst wall may contain

intramural odontogenic epithelial remnants

Occasionally, intraosseous cysts are lined by

orthokeratinized epithelium, thus having the

appearance of an epidermoid cyst (Fig 2.30 )

Such cysts are known as orthokeratinized

odontogenic cyst and their differentiation from

the keratocystic odontogenic tumor with keratinization is clinically relevant as recur-rence of the orthokeratinized cysts is rare whereas the genuine keratocystic odontogenic tumor usually does when not treated properly [ 32 ] Rarely, keratocystic odontogenic tumor shows development of epithelial dysplasia and squamous cell carcinoma [ 33 ]

When infl amed, the keratocystic odontogenic

tumor loses in part its typical histologic

fea-tures, and shows a non-keratinizing stratifi ed

epithelium of varying thickness and exhibiting

spongiosis and elongated rete pegs with an

underlying connective tissue containing a mixed

infl ammatory infi ltrate (Fig 2.31 ) Those cases

may erroneously be diagnosed as a radicular

cyst However, keratocystic odontogenic tumors

usually occupy larger areas of the jaw and are

not confi ned to the periapical tooth region

Moreover involved teeth not necessarily are

avi-tal or at least decayed as in case of a radicular

cyst Hence, there is a discrepancy between

clinical features and radiology at one side and

the histology at the other side and this should

raise suspicion about the representativity of the

material submitted for histology It has to be

stressed that overlooking a keratocystic

odonto-genic tumor may have serious consequences as

they tend to recur after enucleation [ 19 – 21 ],

whereas a resection offers a much higher chance

of permanent cure [ 34 ]

The keratocystic odontogenic tumor may

sometimes be diffi cult to distinguish from

uni-cystic ameloblastoma as both lesions show a

con-spicuous basal cell layer characterized by

hyperchromasia and some palisading However,

keratocystic odontogenic tumor exhibits a pact spinous layer and a corrugated superfi cial parakeratin layer while ameloblastoma shows a spinous layer with intercellular edema and no superfi cial keratinization

com-2.4 Non-odontogenic Cysts

Nasopalatine duct cysts arise within the atine canal from epithelial remnants of the naso-palatine duct As a consequence of this, they exclusively occur in the anterior part of the max-illa, located between the roots of maxillary cen-tral incisor teeth (Fig 2.32 )

nasopal-The cyst may be lined by pseudostratifi ed columnar ciliated epithelium, stratifi ed squamous epithelium, columnar or cuboidal epithelium or combinations of these (Fig 2.33 ) So, this histol-ogy is not very specifi c or helpful in making a diagnosis Specifi c diagnostic details however are provided by the stromal component As surgi-cal treatment comprises emptying the nasopala-tine canal, the specimen always includes the artery and nerve that run in this anatomic struc-ture These are seen within the fi brous cyst wall and form the most convincing diagnostic feature (Fig 2.34 )

Fig 2.31 The typical

histological appearance of a

keratocystic odontogenic

tumor will disappear in case

of concomitant infl ammation

of the cyst wall, transforming

into a non-specifi c spongiotic

squamous epithelium

2.4 Non-odontogenic Cysts

In case of secondary infl ammation, a atine cyst may be mistaken for a radicular cyst However, this diagnosis requires that at least one

nasopal-of the adjacent maxillary teeth shows decay with pulp necrosis because radicular cysts arise as a complication of infl ammatory changes in the periapical root area Such infl ammatory changes only occur as a sequel of tooth pulp pathology and therefore, cysts without associated tooth pathology must be developmental and not infl am-matory So, the condition of the teeth in the involved area allows the differentiation between the infl ammatory radicular cyst and the develop-mental nasopalatine cyst, even if they are histo-logically indistinguishable as a result from extensive infl ammatory changes

2.4.1 Surgical Ciliated Cyst

Surgical ciliated cysts arise from detached tions of the mucosa that line the maxillary antrum that are buried within the maxillary bone This may occur after trauma or surgical intervention in this area [ 35 ] The cyst lining of this cyst is simi-lar to the normal mucosal surface of the paranasal cavities: pseudostratifi ed ciliated columnar epithelium with interspersed mucous cells

Fig 2.32 Radiographic appearance of nasopalatine duct

cyst: radiolucent lesion in the anterior maxilla between

the two central incisor teeth that do not show signs of

decay If the adjacent teeth show signs of decay, this

radio-logic appearance could indicate a radicular cyst as well

Compare with Fig 2.1 showing also radiolucency in

ante-rior maxilla but in this case, involved teeth are diseased as

shown by endodontic treatment

Fig 2.33 Cyst lining of

nasopalatine duct cyst

composed of epithelium

intermediate between

squamous and columnar

Goblet cells and ciliated

columnar cells also may be

found

Therefore, this diagnosis may explain why

graphs may show a well-defi ned unilocular

radio-lucency adjacent to the maxillary antrum whereas

by histology, only normal respiratory mucosa is

observed

2.5 Pseudocysts

2.5.1 Solitary Bone Cyst

The solitary bone cyst , also known as traumatic

bone cyst or simple bone cyst is a unilocular

cav-ity confi ned to the mandibular body (Fig 2.35 )

Its pathogenesis still is poorly understood, a

rem-nant of intraosseous hemorrhage being the most

favored hypothesis

Material for histologic examination may be

diffi cult to obtain as a soft tissue lining of the

bony cavity may be entirely absent or very thin If

present, it usually consists only of loose fi

brovas-cular tissue, although it may also contain

granu-lation tissue with signs of previous hemorrhage

such as cholesterol clefts and macrophages

loaden with iron pigment (Fig 2.36 ) [ 36 ]

Incidentally, threadlike calcifi cations also can be

found (Fig 2.37 ) Sometimes, this lesion may

occur simultaneously with a variety of

fi bro- osseous lesions [ 37 ] but the possibility that

in these cases, one deals with pseudocystic mal degeneration in an ossifying fi broma cannot

stro-be ruled out for certain Most often, histology is more valuable in ruling out other entities that cause unilocular radiolucent jaw lesions then in confi rming the diagnosis of solitary bone cyst

Fig 2.34 Wall of

nasopala-tine duct cyst showing a

conspicuous neurovascular

bundle that represents the

content of the nasopalatine

duct This is the most typical

diagnostic feature for

nasopalatine duct cysts

Fig 2.35 Radiograph of a solitary bone cyst presenting itself through mandibular expansion In spite of this expansion, material for histology may be scanty

2.5 Pseudocysts

2.5.2 Focal Bone Marrow Defect

The focal bone marrow defect represents an

asymptomatic radiolucent lesion of the jaws,

which is due to a localized area of osteoporotic

bone, sometimes following tooth extraction and

that contains normal hematopoietic and fatty

bone marrow It is also called osteoporotic bone

marrow defect This condition is mostly seen at

the angle of the mandible and on biopsy, the ple consists of normal hematopoietic marrow [ 38 ] Awareness of this diagnostic possibility is needed to make the correct clinicopathological correlation between radiology and histology Otherwise, a biopsy of something that looks like

sam-a cyst on rsam-adiogrsam-aphs but only showing normsam-al

Fig 2.36 The lining of a

solitary bone cyst most often

is composed of scanty

fi brous tissue with fi brin

making harvesting material

for histology from this lesion

diffi cult

Fig 2.37 Occasionally,

osteoid depositions with

irregular and threadlike

mineralization may be found

in the wall of a solitary bone

cyst