CD5 expression in neoplastic large B-cells in T-cell/histiocyte-rich large
B-cell lymphoma has not been reported, to the best of our knowledge. Here we describe the first case of CD5+ T-cell/histiocyte-rich large
B-cell lymphoma that is well documented by histomorphology, immunohistochemistry, flow cytometry immunophenotyping and sorting, and
immunoglobulin heavy-chain gene rearrangement study by polymerase chain reaction. The expression of CD5 in large neoplastic B-cells was demonstrated by immunohistochemistry and multicolor flow cytometry. The clonal nature of the CD5+ neoplastic B-cells was confirmed by rearranged
immunoglobulin heavy (IgH) chain with polymerase chain reaction (PCR) of flow cytometry-sorted CD5+/CD19+/kappa+ cells. The CD5+ neoplastic large B-cells expressed bcl-6 and MUM1/IRF4 but not CD138 by immunohistochemistry. This suggests that the neoplastic cells may be of late germinal-center B-cell/ early post-germinal center B-cell origin. The patient responded to
chemotherapy, CHOP (
Cytoxan,
doxorubicin,
vincristine, and
prednisone), and
Rituxan very well and is currently
in complete remission clinically. We propose that the current case, CD5+ T-cell/histiocyte-rich large
B-cell lymphoma, represents a variant of recently reported de novo CD5+ diffuse large
B-cell lymphomas. Our patient has had an excellent response to treatment; however, the clinical and
biologic significance of CD5 expression in T-cell/histiocyte-rich large
B-cell lymphoma requires further studies. Awareness of the CD5+ T-cell/histiocyte-rich large
B-cell lymphoma variant will prompt pathologists to perform CD5 immunohistochemical
stain in cases of T-cell/histiocyte-rich large
B-cell lymphoma. This will lead to identifying more cases to understand the clinical and
biologic characteristics of this variant.