Heterogeneity of cutaneous T-cell lymphoma. Phenotypic and ultrastructural characterization of four unusual cases.

This study characterized, by means of immunocytochemistry and electron microscopy, four cases of "unusual" cutaneous T-cell lymphoma (CTCL) other than classical mycosis fungoids and Sézary syndrome. Cases 1, 2, and 4 were diffuse lymphoma of a pleomorphic type, and Case 3 was of a mixed type. Case 4 shared a feature common to pagetoid reticulosis. A fairly large number of inflammatory cells were seen in Cases 1, 3, and 4. Functionally, the neoplastic cells of Cases 1, 3, and 4 were of a helper/inducer T-cell subset, whereas those of Case 2 were of a suppressor/cytotoxic T-cell type. Epidermotropic cells with pagetoid growth in Case 4 failed to show these specific surface phenotypes, although they still retained pan T-cell markers. Neoplastic large or intermediate-sized cells revealed a marked difference in the development of cytoplasmic organelles and their nuclear profiles, ranging from a few simple indentations (Cases 2 and 3) to forms with many deep indentations (Case 1) and highly cleaved shapes (Case 4). All of these cells, however, possessed dense-cored granules located in a portion of the cytoplasm. This study indicated the clinicopathologic and immunologic heterogeneity of CTCL, which may be classified, according to the reactivity with monoclonal antibodies and the fine structural features, into subtypes that correspond to functionally distinct subsets of T-cells and their stages or types of differentiation.