Peripheral T-cell lymphoma complicated by a proliferation of large B cells

We studied 14 cases that showed a morphologic appearance of peripheral T-ce ll lymphoma and contained substantial numbers of CD20+ targe B cells. In al l but 2 cases, the CD20+ large cells showed a mix of kappa and lambda light chain expression. Two cases showed a focal predominance of kappa expressio n. ln situ hybridization using the EBER1 probe for detection of Epstein-Bar r virus (EBV) RNA was performed on every case. EBV RNA Mras present in 10 c ases. Of 8 cases with EBV RNA stained by immunohistochemistry for the laten t membrane protein of EBV, 6 were positive. Double-labeling immunohistochem istry and in situ hybridization confirmed that EBV was present in the large B cells. Polymerase chain reaction (PCR) analysis showed a clonal rearrang ement of the T-cell receptor (TCR)-gamma chain gene in 12 of 13 cases teste d. One additional case showed a clonal rearrangement of the TCR-beta chain gene bq Southern blot hybridization. PCR analysis showed a clonal immunoglo bulin gene rearrangement in 5 cases, a suggestion of a clonal rearrangement in I, an oligoclonal pattern in 4, and a polyclonal pattern in 4. The find ing of large B and T cells may result in a misdiagnosis of a reactive proce ss or of T-cell-rich B-cell lymphoma. The presence of EBV in some cases cou ld cause further confusion with the reactive T- and B-immunoblastic prolife ration of infectious mononucleosis.