Round cells of the epidermis: clues from studies on neoplastic lymphocytes of cutaneous T cell lymphoma.

Neoplastic cells of cutaneous T cell lymphoma (CTCL) appear to be of monoclonal origin and frequently are nonspecific helpers of normal B cell differentiation. A natural progression from epidermotropic (mycosis fungoides and Sézary syndrome) to nonepidermotropic, more widely disseminated T cell neoplasms generally occurs. Affinity of CTLC cells for the epidermis may result from their having membrane receptors for histocompatibility (Ia) antigens present in skin. Cultured human epidermal cells produce a thymopoietin-like molecule, an indication of a role for skin in T cell differentiation.