Primary Cutaneous Natural Killer Cell Blastic Lymphoma

An 81 yo male presented with several asymptomatic firm 1–5 cm red purple plaques on the trunk and lower extremities associated with a mild pancytopenia. Histological examination revealed a diffuse, monotonous dermal infiltrate of atypical medium sized cells with fine chromatin and scanty cytoplasm. Immunoperoxidase staining demonstrated positivity for CD 45, CD43, CD4, Bcl‐2, and TdT; but was negative for cytokeratin, melan‐A, CD30 and hematopoietic lineage specific markers. A subsequent bone marrow aspirate demonstrated a dense population of cells that were morphologically consistent with blasts. Immunophenotyping by flow cytometry revealed lesional cells that expressed CD56, CD4, CD7, CD5, HLA‐DR and TdT. However, lineage specific markers for B‐cells (CD19, CD20, cCD79a, and CD10), T‐cells (sCD3 and cCD3), and myeloid cells (CD13, CD33, CD117, cCD13, CD14, CD41, CD61, myeloperoxidase, and alpha napthyl butyrate esterase) were not expressed. Molecular studies by PCR exhibited no evidence of T‐cell receptor or heavy chain gene rearrangements. Collectively, these findings are consistent with a primary cutaneous blastic natural killer cell lymphoma. Blastic natural killer cell lymphomas are characterized by a high incidence of cutaneous involvement and an aggressive clinical course. Our patient responded dramatically to one cycle of CHOP chemotherapy with resolution of his cutaneous tumors.