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...
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Chapter 083. Cancer of the Skin (Part 5) Chapter 083. Cancer of the Skin (Part 5) A lifetime risk of melanoma development of 6% has been estimated. Therisk is greatest before age 5 and next greatest between ages 5 and 10. Earlydetection of melanoma is difficult in these lesions because of the deep dermal orsubcutaneous origin of primary melanoma and because of the large and variedsurface of the nevus. Prophylactic excision early in life can be accomplished bystaged removal with coverage by split-thickness skin grafts. Surgery cannotremove all at-risk nevus cells as some may penetrate into the muscles or centralnervous system below the nevus. At present there are no uniform managementguidelines for giant congenital nevi. The small- to medium-sized congenitalmelanocytic nevus, which affects approximately 1% of persons, usually presents asa 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-pepperconfiguration. The lesion may have an excess of thick, coarse hairs. The risk ofmelanoma developing in these lesions is not known but appears to be relativelysmall. The management of small- to medium-sized congenital melanocytic neviremains controversial. Melanomas in small congenital melanocytic nevi appear tooccur after puberty, unlike melanomas that arise in giant congenital nevi and tendto occur much earlier in life. Melanomas can also arise in benign dermal andcompound 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 yearsis 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 lesionsfrom melanoma and its precursor. If melanoma is a consideration, then biopsy isappropriate. Some benign look-alikes may be removed in the process of trying todetect authentic melanoma. Table 83-5 summarizes the distinguishing features ofbenign lesions that may be confused with melanoma. Early detection of melanomamay be facilitated by applying the ABCD rules: A—asymmetry, benign lesionsare 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 isdiameter >6 mm since a significant fraction of melanomas are now diagnosed withdiameters recognition of nodular melanomas, which may be symmetrical and have uniformcolors. Different has been substituted for diameter by some. Addition of anE for evolution has been proposed as other features may become moresignificant if the lesion is changing. Table 83-5 Pigmented Lesions that Must Be Distinguished fromCutaneous 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 Junctional Flat to barely raised brown lesion. Sharp border.nevus Fine pigmentary stippling visible, especially upon magnification. Lentigo Flat, uniformly medium or dark brown lesion with sharp border. Solar lentigines are acquired lesions on sites Juvenile of chronic solar exposure (face and backs of hands). Solar Lesions are 2 mm to ≥1 cm. Solar lentigines have reticulate pigmentation upon magnification. Pigmented basal Papular border. May have central ulceration.cell carcinoma Usually on a sun-exposed surface in an older patient. Patient usually has dark brown eyes and dark brown or black hair. Pigmented Lesion is not well demarcated visually, is firm, anddermatofibroma dimples downward when compressed laterally. Usually on extremities. Usually keratosis Presence of keratin plugs in surface is helpful for discriminating especially dark lesions from melanoma. Subungual Maroon (red-brown) coloration. As lesion growshematoma out from nail fold, a curving clear area is seen. Tattoo (medical In medical tattoo, lesions are small pigmentaryor traumatic) dots, often blue or green, which make a regular pattern ...