Site-dependent phenotypic heterogeneity in peripheral T-cell lymphoma.

Peripheral T-cell lymphomas constitute a heterogeneous population of postthymic T-cell malignancies. Characteristically, they present a varied phenotypic expression, which can be helpful in establishing the diagnosis. A case of a peripheral T-cell lymphoma in a 76-year-old man is described. The malignant cells in the skin and bone marrow were of the T4 (helper/inducer) phenotype, yet they did not express pan-T-cell antigens, such as T11, or functional E rosettes. In a biopsy specimen from a lymph node, however, the malignant cells had a helper/inducer phenotype and also expressed the pan-T-cell antigens T11 and Leu-5. Additionally, the malignant cells from the lymph node formed E rosettes. This study demonstrates the phenotypic heterogeneity of malignant T cells, which appears to be site-dependent.