A case of a Ki-1 large cell anaplastic lymphoma with ultrastructural features.

A 29-year-old woman first presented in 1982 with a large cell lymphoma, initially thought to be of histiocytic origin on the basis of prominent sinus infiltration. She had a complete response to chemotherapy, but relapsed in 1987. Histologically, a repeat biopsy was identical to the first. Immunocytochemically, there was strong reactivity with Ki-1 antibody and histiocyte lineage markers, but all specific T cell markers were negative. Southern blot hybridization demonstrated a clonally rearranged band with the T cell receptor (T beta) probe. Ultrastructurally, the cells showed sparse organelles except for prominent paranuclear Golgi apparatus, frequent reniform nuclear indentations, and ruffled cytoplasmic membranes. This case appears to represent a Ki-1-positive lymphoma with the hybrid features of an activated T lymphocyte and a histiocyte.