Neoplastic Epidermotropic Diseases

Abstract

Mycosis fungoides (MF) and Sézary syndrome (SS) together comprise 65 % of cutaneous T-cell lymphomas (CTCL). MF has protean clinical appearances at presentation and throughout its clinical course. An individual patient can manifest more than one clinical lesion simultaneously and as the disease progresses. Here we describe morphologic and clinical features of early and advanced stages of MF, clinical variants of MF, and the closely related SS. Illustrated histologic hallmarks are helpful in distinguishing early MF from cutaneous inflammation. Histologic and clinical laboratory biomarkers for the prognosis of MF patients are discussed. Cutaneous manifestations of other epidermotropic T-cell malignancies, adult T-cell leukemia/lymphoma, primary cutaneous gamma-delta T-cell lymphoma, as well as clinically benign LyP are described. It should be emphasized that various benign reactive epidermotropic disorders can closely mimic MF and SS. Some benign disorders, e.g., drug eruptions, contact dermatitis, and HIV-related atypical skin infiltrates, can be excluded by clinical history. Histologic features more common in benign disorders are epidermal spongiosis and hypergranulosis and dermal eosinophils or plasma cells. Benign disorders, e.g., actinic reticuloid, annular lichenoid dermatitis of youth, HIV-related CD8+ atypical skin infiltrates, and pityriasis lichenoides, are more commonly associated with a predominance of CD8+ cells; numerous B cells are present in lymphomatoid lichenoid keratosis. The presence of a T-cell clone is supportive of lymphoma but can be seen in some benign epidermotropic T-cell disorders and must be interpreted in context of clinical and histologic features.