T-CELL RICH B-CELL LYMPHOMA PRESENTING IN SKIN - A CLINICOPATHOLOGICAL ANALYSIS OF 6 CASES

We reviewed our experience with six T-cell-rich B-cell lymphomas (TRBL ) presenting in skin. Immunohistochemical studies were performed on al l biopsies. The lymphoid population consisted mainly of CD3 and/or UCH L-1 (CD45RO) positive T cells. 5 to 15% of the lymphoid cells stained for the B-cell marker L26 (CD20). Monoclonality of the B-cell componen t was demonstrated in all cases, utilizing either light chain restrict ion (5 cases) or clonal immunoglobulin heavy chain gene rearrangement by polymerase chain reaction (PCR) (2 cases). One case tvas confirmed to be monoclonal by both techniques. Additionally, no clonal rearrange ments of the T-cell receptor gamma gene were observed. There was consi derable morphological variety in these cases. In H&E stained sections, the differential diagnosis included pseudolymphoma, peripheral T-cell lymphoma, Hodgkin's disease, Lennert's lymphoma and a MALT lymphoma. A significant component of monoclonal plasma cells was present in 3 of 6 cases, suggesting a possible origin from cutaneous immunocytoma. In fact, one of our cases was a biphasic lymphoma displaying TRBL with a small focus of immunocytoma. We conclude that immunophenotypic analys is is necessary for the diagnosis of TRBL. Pathologists should be awar e of this type of cutaneous B-cell lymphoma to avoid misinterpretation as a pseudolymphoma.