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-g ray. 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 pa pillomatous; 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 bord er. 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 us ually 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-bo rdered 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 t attoos are irregular, and pigmentation may appear black. . 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. 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. 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