04 Malignant Skin Lesions

E radial versus vertical and the depth of

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Unformatted text preview: cific subtype a tumor falls into, in itself, is not as important as the pattern of growth (i.e., radial versus vertical) and the depth of penetration.30 The main subtypes are lentigo maligna melanoma, superficial spreading melanoma, acral lentiginous melanoma, and nodular melanoma. Of these, superficial spreading melanoma is the most common, accounting for more than 70% of melanomas. These lesions occur most frequently in white adults, typically on the back or the legs. Nodular melanoma is the second most common subtype, accounting for between 15% and 30% of all melanomas.These lesions often appear dome-shaped and may occur anywhere on the body.They typically manifest an early vertical growth phase and thus tend to invade the dermis early in their natural history. Lentigo maligna melanoma accounts for approximately 5% of all melanomas and is believed to arise in a focus of lentigo maligna (Hutchinson freckle). These lesions demonstrate a prolonged radial growth phase before exhibiting an invasive component. Acral lentiginous melanoma occurs on the hands or the feet [see Figure 3b], often under the nailbed, where the dermis is thinner (subungual melanoma).There also exists a relatively rare histologic subtype known as desmoplastic melanoma, which typically occurs in areas of sun damage and tends to recur locally more often than other subtypes do. Staging and Prognosis An important variable in the prognosis of melanoma is the thickness of the primary tumor, as assessed by means of either the Bres- I Epidermis Papillary Dermis Reticular Dermis Subcutaneous Fat II III IV low system or the Clark system [see Table 2]. In the Breslow system, a calibrated ocular micrometer is employed to measure tumor thickness from the epidermal surface to the deepest point of the tumor’s extension into tissue.31 In the Clark system, the levels are defined by the presence or absence of malignant melanocytes in each of the following layers: epidermis, papillary dermis, reticular dermis, and subcutaneous fat [see Figure 4].32 Over the past several years, extensive research has been conducted on factors that affect prognosis in both early-stage and late-stage melanoma. Clinical factors that have been shown to possess significant prognostic value include age, sex, the location of the melanoma, the number of lymph nodes involved, the presence of distant metastasis, and the serum lactate dehydrogenase (LDH) level.33 In general, the prognosis is better when the patient is younger than 65 years of age, when the patient is female, when the tumor is located on an extremity, when no lymph nodes are involved, when there is no evidence of distant metastasis, and when the serum LDH level is normal. Melanomas are usually staged according to the system developed by the American Joint Committee on Cancer (AJCC), the latest version of which was approved in 2002 [see Tables 3 and 4].34 The AJCC stage correlates well with the 5-year survival rate [see Table 5].34 Stage I and II melanoma The vas...
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