Phenotypic characterization of lymphocyte subsets in mycosis fungoides. Comparison with large plaque parapsoriasis and benign chronic dermatoses.

Altogether, 209 skin biopsies from 103 patients with mycosis fungoides (MF), large plaque parapsoriasis (LPP), and benign chronic dermatoses (BCD) have been examined immunohistologically with the use of a panel of 21 monoclonal antibodies against lymphoid cells and their subsets. All the infiltrates contained a mixture of T-lymphocytes, Langerhans cells, and other types of HLA-DR-positive dermal macrophages. The neoplastic T-cells in MF lesions expressed proliferation-(transferrin receptor) and activation-(the OKT10 antigen) associated markers more frequently than the T-cells in LPP and BCD. In other respects, the neoplastic T-cells in plaque lesions of MF resembled those seen in LPP and BCD; and most of these cases demonstrated a clear predominance of T-cells of helper/inducer type. The neoplastic T-cells in tumor lesions of MF were much more heterogeneous in phenotype. Only eight of these cases could be classified as T-helper neoplasms. In the remaining ten tumor cases, the neoplastic cells expressed either suppressor/cytotoxic or aberrant T-cell phenotypes. There were no phenotypic differences between the "classical" tumor stages and MF d'emblee cases. The data indicate that the early lesions of MF show an immunohistologic reaction pattern common to many immune responses of the skin and that the neoplastic cells in the advanced stages are more heterogeneous in phenotype than previously recognized.