Plasmacytoid monocyte proliferation associated with myeloproliferative disorders

Plasmacytoid T-cell (PTC) lymphoma is a rare clinicopathologic entity characterized by generalized lymphadenopathy in association with a myeloproliferative disorder. Hepatosplenomegaly and weight loss frequently are present. Nodal T-zone expansion by mononuclear cells with ultrastructural and immunohistochemical features typical of PTC is diagnostic. All of the five previously reported cases of PTC lymphoma coincided with or heralded the onset of a clinically aggressive myeloid leukemia. This strong association and recent immunohistochemical findings in reactive or neoplastic PTC favored a monocyte/macrophage derivation of these cells, and it has been suggested that they be renamed plasmacytoid monocytes (PM). Two additional cases of PTC lymphoma were studied at the institutions of the authors, and the findings supported the concept that PTC belong to the monocytic lineage. The disease presentation was generalized lymphadenopathy with constitutional symptoms. One patient also had hepatosplenomegaly and bilateral renal enlargement concomitantly with myelofibrosis with myeloid metaplasia that progressed within months to acute myelogenous leukemia. Similar rapid evolution of acute monoblastic leukemia occurred in the other patient. Tumor cells within subtotally effaced lymph nodes had positive findings for CD45, CD4, CD7, and LN2 and negative findings for CD3, CD8, and beta F1. Occasional cells had positive findings for CD2. One case demonstrated CD5, HLA-DR, CD71, and CD43 (Leu-22)-positive cells. The myeloid/monocyte-associated antigens CD14 and CD68 were identified in both. The tumor cells lacked the B-cell markers LN1, CD20 (L26), CD19, and CD22 and did not rearrange immunoglobulin heavy chain genes and T-cell receptor beta, gamma, and delta chain genes. The term plasmacytoid T-zone lymphoma or PM proliferation is more appropriate for this rare disease. The close association of the PM proliferation with a myeloproliferative disorder indicates that the two entities are related.