BONE-MARROW INVOLVEMENT IN T-CELL-RICH B-CELL LYMPHOMA

We describe the histologic and immunohistochemical findings in specime ns from bone marrow (BM) biopsies performed for staging purposes in 13 patients with a previous tissue-based diagnosis of T-cell-rich B-cell lymphoma (TCRBCL). Bone marrow involvement was found in 8 (62%) of 13 cases and was often paratrabecular. The histologic appearance was not pathognomonic of TCRBCL, with the differential diagnosis including Ho dgkin's disease and peripheral T-cell lymphoma. The infiltrates typica lly had a pale low-power appearance (due to histiocytic infiltration, relative hypocellularity, or both) that, in conjunction with the prese nce of a polymorphous infiltrate of scattered large atypical cells ami d a mixed infiltrate of small lymphocytes and histiocytes, was suggest ive of Hodgkin's disease. Immunohistochemistry revealed CD20 reactivit y of the large atypical cells with the absence of CD15 and CD30 reacti vity, supporting the diagnosis of TCRBCL. A prominent small T-cell inf iltrate accompanying the large atypical cells was observed in all posi tive BM biopsy specimens. The increased incidence of BM involvement in TCRBCL is significantly higher than that found in de novo B-cell diff use large cell lymphoma, suggesting a possible biologic difference bet ween the two entities. Our cases share some similar clinicopathologic features with histiocyte-rich B-cell lymphoma and with diffuse lymphoc yte-predominant Hodgkin's disease, paragranuloma type. We discuss the possible relationship to these two entities.