Lymph node interdigitating reticulum cell sarcoma.

A 67-year-old man presented with a malignant tumor involving abdominal lymph nodes, spleen, liver, and lungs, with associated protracted fever and night sweats. The tumor consisted of large pleomorphic cells, often surrounding microabscesses. Intracytoplasmic S100 protein, surface T6, Leu-3a (T4), and HLA-DR antigens were demonstrated. The malignant cells also possessed ATPase activity. Ultrastructurally, the cells exhibited numerous interdigitating cell processes but no Birbeck granules. The anatomic distribution of the tumor, its ultrastructural features, immunologic phenotype, and enzymatic profile are all consistent with a derivation from lymph node interdigitating reticulum cell. The tumor was unresponsive to the chemotherapeutic agents administered, and the patient soon died.