Mycosis fungoides and Sézary's syndrome show distinct histomorphological features.

A light microscopic investigation of skin biopsy specimens from 10 patients with plaque stage mycosis fungoides (MF) and from 6 with Sézary's syndrome (SS) was carried out according to the defined histologic criteria, for the purpose of detecting some morphological characteristics of these diseases for their histological differentiation. This study revealed that some histomorphological differences regarding the epidermal and dermal changes, epidermotropism and the cellular infiltrate existed between MF and SS, and that these diseases were two distinct entities showing differences not only from a clinical and hematologic but also from the histological viewpoint.