Primary cutaneous natural killer/T-cell lymphoma of the nasal type: a report of 4 cases in North American patients.

The "nasal" type of primary cutaneous lymphoma with natural killer/T-cell differentiation is rarely encountered outside Asia. The authors herein document 4 cases in White, North American individuals between the ages of 39 and 73 years. Their skin lesions were located on the legs in 2 cases, and they were multifocal in the other 2 patients. Microscopically, each neoplasm manifested as a dense infiltrate of cytologically aberrant lymphocytes in the dermis and subcutis. The lesional cells were angiocentric, with associated infarctive-type necrosis of the surrounding tissue. All tumors were labeled for CD3 and CD56; 3 also expressed T-cell intracellular antigen 1. Chromogenic in situ hybridization was intensely reactive for Epstein-Barr virus-encoded ribonucleic acid in each case. All patients died of their tumors or were likely to do so. The pathologic differential diagnosis of "nasal-type" natural killer/T-cell lymphoma in the skin principally centers on γ-δ T-cell lymphoma and subcutaneous panniculitis-like T-cell lymphoma. Integrated analysis of histologic, immunohistochemical, genotypic, and in situ hybridization data is necessary to separate these entities from one another.