Unusual biclonal plasma cell dyscrasia with crystallike inclusions producing colonic tumors (plasma cell polyposis) and terminating in T-cell lymphoma.

A 62-year-old man underwent a partial colectomy for persistent rectal bleeding. Multiple submucosal lesions up to 7 cm in diameter were identified and were composed of plasmacytoid and histiocytoid cells with crystallike inclusions. Ultrastructurally, inclusions were bounded by rough endoplasmic reticulum. Immunohistochemical studies demonstrated a monoclonal population of IgA kappa-positive plasma cells. Immunofixation using a saline extract of the tumor revealed two distinct bands: one for IgG kappa and another for IgA kappa. Southern blotting revealed a germline configuration for the immunoglobulin heavy-chain gene and the T-cell antigen receptor beta-chain gene. A bone marrow aspirate contained 12% plasma cells, some of which had cytoplasmic inclusions. Eight months after surgery, the patient developed a large mediastinal mass. Histologic and immunohistochemical studies indicated that this mass was an undifferentiated neoplasm. However, gene rearrangement studies indicated a T-cell lymphoma. This patient illustrates a rare association between a plasma cell neoplasm and a T-cell lymphoma.