The immunologic and clinicopathologic heterogeneity of cutaneous lymphomas other than mycosis fungoides.

Twenty-one cases of non-Hodgkin's lymphoma with cutaneous involvement, other than mycosis fungoides, were evaluated immunologically, histologically, and clinically. Ten patients presented with skin disease alone, seven with concurrent cutaneous and extracutaneous disease, and four with extracutaneous disease only. Twenty of the 21 cases were nonepidermotropic tumors and were equally likely to express B or T phenotypes. None of the cases expressed a true histiocytic phenotype. Almost all cases expressed la and class 1 HLA determinants. Immunophenotypes were stable regardless of time interval, therapy, or body site sampled in seven of eight patients studied serially. In contrast to mycosis fungoides, the T lymphomas exhibited noncerebriform cytology, tumor la expression, lack of mature helper T-cell phenotype, nonepidermotropic histology, a tendency for marrow involvement, and presented as nodules rather than patches or plaques. Since each T lymphoma expressed an abnormal but uniform T-cell phenotype other than mature cytotoxic/suppressor or helper, the neoplastic population could be distinguished from reactive T cells. Reactive elements averaged one-third of the cellular infiltrates and were mainly T cells and macrophages. Langerhans cells were generally normal in number and distribution. Several histopathologic subtypes were identified with diffuse large cell lymphomas, including immunoblastic lymphomas, comprising 71% of cases (15/21). Prediction of the immunophenotype based on cytologic criteria was correct in 67% of cases (14/21). All errors occurred among the 13 high-grade lymphomas. Survival data were consistent with those of prior studies that have indicated that clinical course is dependent on stage and histologic subtype. Non-Hodgkin's cutaneous lymphomas constitute an immunologically, histologically, and clinically heterogeneous group of neoplasms.