Composite cutaneous T-cell lymphoma and small B-cell lymphocytic lymphoma: morphologic, immunologic, and molecular genetic documentation of concurrent lymph node involvement.

Synchronous cutaneous T-cell lymphoma and low-grade B-cell lymphoproliferative disorders have rarely been reported in the same patient. Coexpression of each phenotype in the same lymph node has not, to our knowledge, been previously documented. We describe an 86-year-old man with chronic pruritus and erythroderma and recent-onset peripheral lymphadenopathy and lymphocytosis. Lymph node biopsy provided morphological and immunohistochemical evidence of concurrent small B lymphocytic lymphoma and small pleomorphic T-cell lymphoma. Immunophenotyping of nodal lymphocytes demonstrated two distinct clones: IgM-kappa B-cells with CD5 positivity and CD7 negative T-helper cells. Both immunoglobulin (heavy and light chains) and T-cell receptor (beta I and beta II) gene rearrangements were detected by Southern blot analysis of the lymph node. In contrast, the immunophenotype of lymphocytes from peripheral blood and bone marrow was exclusively that of T-helper cells with atypical CD7 deletion. Electron microscopic examination of circulating lymphocytes revealed small cerebriform Sezary cells. This case demonstrates that small lymphocytic lymphoma may coexist intranodally with cutaneous T-cell lymphoma as a unique form of composite T- and B-cell lymphoma.