We reported a case of cutaneous NK cell lymphoma. A 63 year-old woman had a solitary tumor on the right side of her back two years ago. Gradually the tumor developed. The biopsy showed dense infiltration of abnormal lymphocytes in the dermis and subcutaneous tissue. Those abnormal lymphocytes are large and had atypical nuclei and mitosis. Destructive infiltration to blood vessels was not observed. The immunophenotype was positive for CD56 and negative for other T cell and B cell histiocytic markers. The immunogenotype showed germline configurations for immunoglobulin heavy chain gene and T cell receptor gene. In situ hybridization using the anti-sense EBER RNA probe revealed negative. She received radiation and chemotherapy. After these treatments, the tumor sized down and disappered. [Skin Cancer (Japan) 2001; 16: 67-71]
