Chapter 083. Cancer of the Skin (Part 5) ppsx

Early detection of melanoma is difficult in these lesions because of the deep dermal or subcutaneous origin of primary melanoma and because of the large and varied surface of the nevus..

Chapter 083 Cancer of the Skin

(Part 5)

A lifetime risk of melanoma development of 6% has been estimated The risk is greatest before age 5 and next greatest between ages 5 and 10 Early detection of melanoma is difficult in these lesions because of the deep dermal or subcutaneous origin of primary melanoma and because of the large and varied surface of the nevus Prophylactic excision early in life can be accomplished by staged removal with coverage by split-thickness skin grafts Surgery cannot remove all at-risk nevus cells as some may penetrate into the muscles or central nervous system below the nevus At present there are no uniform management

guidelines for giant congenital nevi The small- to medium-sized congenital melanocytic nevus, which affects approximately 1% of persons, usually presents as

a raised dark- to medium-brown lesion with a smooth or papillomatous surface The border is sharp, and lesions may be oriented along lines of skin cleavage Follicular hyper- and hypopigmentation may coexist in a salt-and-pepper

configuration The lesion may have an excess of thick, coarse hairs The risk of melanoma developing in these lesions is not known but appears to be relatively small The management of small- to medium-sized congenital melanocytic nevi remains controversial Melanomas in small congenital melanocytic nevi appear to occur after puberty, unlike melanomas that arise in giant congenital nevi and tend

to occur much earlier in life Melanomas can also arise in benign dermal and compound moles Overall, it has been estimated that for a 20-year-old individual, the lifetime risk of any selected mole transforming into melanoma by age 80 years

is approximately 0.03% (1 in 3,164) for men and 0.009% (1 in 10,800) for women

Differential Diagnosis

The aim of differential diagnosis is to distinguish benign pigmented lesions from melanoma and its precursor If melanoma is a consideration, then biopsy is appropriate Some benign look-alikes may be removed in the process of trying to detect authentic melanoma Table 83-5 summarizes the distinguishing features of benign lesions that may be confused with melanoma Early detection of melanoma may be facilitated by applying the "ABCD rules": A—asymmetry, benign lesions are usually symmetrical; B—border irregularity, most nevi have clear-cut borders; C—color variegation, benign lesions usually have uniform light or dark pigment; D—diameter >6 mm (the size of a pencil eraser) Of these criteria, the weakest is diameter >6 mm since a significant fraction of melanomas are now diagnosed with diameters <6 mm In addition, the above features are less helpful in the

recognition of nodular melanomas, which may be symmetrical and have uniform colors "Different" has been substituted for "diameter" by some Addition of an

"E" for evolution has been proposed as other features may become more significant if the lesion is changing

Table 83-5 Pigmented Lesions that Must Be Distinguished from Cutaneous Melanoma and Its Precursors

Blue nevus Gunmetal or cerulean blue, blue-gray Stable over

time One-half occur on dorsa of hands and feet Lesions are usually single, small, 3 mm to <1 cm Must be distinguished from nodular melanoma

Compound

nevus

Round or oval shape, well-demarcated, smooth-bordered May be dome-shaped or papillomatous; colors range from flesh colored to very dark brown, with individual nevi being relatively homogeneous in color

Hemangioma Dome-shaped reddish, purple, blue nodule

Compression with a glass microscope slide may result in blanching Must be distinguished from nodular melanoma

Junctional

nevus

Flat to barely raised brown lesion Sharp border Fine pigmentary stippling visible, especially upon magnification

Lentigo

Juvenile

Solar

Flat, uniformly medium or dark brown lesion with sharp border Solar lentigines are acquired lesions on sites

of chronic solar exposure (face and backs of hands) Lesions are 2 mm to ≥1 cm Solar lentigines have reticulate pigmentation upon magnification

Pigmented basal

cell carcinoma

Papular border May have central ulceration Usually on a sun-exposed surface in an older patient Patient usually has dark brown eyes and dark brown or black hair

Pigmented

dermatofibroma

Lesion is not well demarcated visually, is firm, and dimples downward when compressed laterally Usually on extremities Usually <6 mm

Seborrheic Rough, sharp-bordered lesions that feel waxy and

"stuck on"; range in color from flesh to tan, to dark brown

keratosis Presence of keratin plugs in surface is helpful for

discriminating especially dark lesions from melanoma

Subungual

hematoma

Maroon (red-brown) coloration As lesion grows out from nail fold, a curving clear area is seen

Tattoo (medical

or traumatic)

In medical tattoo, lesions are small pigmentary dots, often blue or green, which make a regular pattern (rectangle) Traumatic tattoos are irregular, and pigmentation may appear black