Cutaneous Lymphomas - Part I: Mycosis Fungoides, Sézary Syndrome, and CD30⁺ Cutaneous Lymphoproliferative Disorders

CD30⁺ primary cutaneous lymphomas comprise a large group of malignant lymphoproliferative disorders that present in the skin without extracutaneous involvement at the time of diagnosis. The incidence of these lymphomas is low, at 7 to 10 cases per 100 000 population. Two types, derived from T cells (70%-85%) or B cells (15%-30%), have been identified. Hematologists and oncologists have increasingly recognized the idiosyncrasy of primary cutaneous lymphomas, as reflected in the updated classification of the World Health Organization. However, there remain nuances or small differences to consider when managing these conditions, obliging dermatologists to continue to strive to fully reconcile the various clinical pictures in future reviews of the classification of lymphoid neoplasms. A diagnosis of a primary cutaneous lymphoma is based on clinical, histopathologic, immunophenotypic, and genotypic criteria, particularly evidence of T- or B-cell lymphoid monoclonality in lesions. Also relevant are complementary tests to rule out extracutaneous involvement.