Clear cells in acral melanoma

Acral melanoma may present clinically and histologically with atypical feat ures causing a delay in proper diagnosis. The aim of the present study was to assess the frequency of a histological variant with clear cell changes. Clinical information, hematoxylin & eosin stained paraffin sections and imm unohistochemical staining profiles were reviewed in 49 cases of acral melan oma. Twenty-one (43%) specimens contained tumor cells with clear cell chang es in focal areas, whereas in 7 (14%) specimens clear cells were the major tumor constituting cells. The tumor thickness ranged from melanoma in situ to 14 mm. Immunohistochemistry demonstrated weak staining for S100 and HMB4 5 as well as strong positivity for Melan A and NK1C3. Recognition of clear cell features is important since differential diagnosis includes a variety of other clear cell malignancies, among them metastasis from renal cell car cinoma, clear cell sarcoma and hidradenocarcinoma.