Primary cutaneous T-cell-rich B-cell lymphomas with flow cytometric immunophenotypic findings - Report of 3 cases and review of the literature

Background.--Primary cutaneous T-cell-rich B-cell lymphoma is a relatively rare entity that has been diagnosed most commonly using immunohistochemical and molecular techniques. Flow cytometric immunophenotyping (FCI) has not been described in this entity. We report the demonstration of B-cell monocl onality by FCI in 3 cases of primary cutaneous T-cell-rich B-cell lymphoma. Methods.--Clinical and pathologic data were recorded for 3 cases of primary cutaneous T-cell-rich B-cell lymphoma. Immunohistochemical and FCI data we re available in all cases; DNA analysis was performed in 1 case. Results.--Flow cytometric immunophenotyping revealed a monoclonal B-cell po pulation exclusively in the monocyte (large cell) region in all 3 cases. Im munohistochemistry confirmed the T-cell richness of the infiltrates within the cutaneous lymphomas; T cells accounted for 65% to greater than 90% of t he cells within the infiltrates. DNA analysis by polymerase chain reaction in 1 case did not demonstrate a monoclonal rearrangement of the immunoglobu lin heavy-chain gene. Conclusions.--Flow cytometric immunophenotyping in primary cutaneous T-cell -rich B-cell lymphoma may be useful in demonstrating monoclonality in these cases, especially if there is selective gating on the relatively small pop ulation of cells in the large cell region. The FCI data should be correlate d with histology and immunohistochemistry.