Morphological variability of tumour cells in T-cell-rich B-cell lymphoma. A histopathological study of 14 cases.

T-cell-rich B-cell lymphoma (TCRBCL) is an unusual lymphoma which is difficult to diagnose. A majority of reactive T-cells and numerous histiocytes mask the few large neoplastic B-cells. Fourteen cases of TCRBCL were studied in order to identify the main histological and cytological features useful for this diagnosis. Neoplastic cells are atypical and sometimes difficult to classify. Several types are seen; they are mostly centroblasts, which represent more than 50% of the tumour cells but are sometimes multilobated, immunoblasts- or Reed-Sternberg-like cells. Interestingly, at least two, and often three, types of tumour cell are present in all the cases. Epithelioid cells and histiocytes are always found and are often numerous. Hypervascularization and fibrosis are present in the majority of cases, but without annular bands. Necrosis is absent. All tumour cells express CD20 but EMA is expressed in less than half the cases. In two cases, the association of a diffuse large B-cell lymphoma in one site and a TCRBCL in another suggests that TCRBCL may be considered as a peculiar pattern of a diffuse large B-cell lymphoma with a strong stroma reaction. TCRBCL may not represent a clinicopathological entity.