Clear Cell Primary Cutaneous Anaplastic Large Cell Lymphoma.

A case of primary cutaneous anaplastic large cell lymphoma that was characterized by a striking clear cell appearance occurring in the thigh of a 38-year-old man is described. The tumor presented as a large ulcer with indurated borders and serosanguinous base measuring 9.0 × 4.0 cm. A biopsy of the lesion showed a dense mononuclear cell infiltrate replacing the dermis and focally infiltrating the epidermis. The infiltrate consisted of nests and sheets of large pleomorphic tumor cells with large atypical nuclei displaying nuclear irregularities with occasional prominent nucleoli. The tumor cells were surrounded by an ample rim of clear cytoplasm imparting them with a clear cell appearance. The cells splayed the collagen in the dermis creating a compartmentalized appearance suggestive of an epithelial neoplasm. Immunohistochemical stains showed positivity of the tumor cells for CD3, CD4, CD30, and CD45RO, and negative staining for cytokeratin AE1/AE3, p63, S-100 protein, ALK-1, PAX5, CD8, CD15, CD20, CD43, and CD56, and Epstein-Barr-encoded RNA test in situ hybridization. A MIB-1 proliferation marker showed nuclear positivity in approximately 40% of the tumor cells. This case is remarkable for its striking clear cell appearance, which may lead to confusion for other tumors. Awareness of this unusual morphologic appearance in anaplastic large cell lymphoma is of important for proper diagnosis and treatment.