New insight into the pathogenesis of Mycosis fungoides and Sérazy syndrome

Primary cutaneous lymphomas are tumors that appear primarily in the skin. The subtypes of the second most common form of extranodal non-Hodgkin’s lymphoma have different clinical, histological, immunological, and molecular characteristics. The most common type of them is mycosis fungoides (MF) and rare its leukemic variant Sézary syndrome (SS). Both diseases are type Th (CD4 +T helper) cells of origin. The development of immunology and molecular biology techniques have significantly expanded our knowledge of pathogenesis. Today, it is proven that MF and SS are derived from different groups of T cells: SS from central memory T cells and MF from skin-resident effector memory T cells. Th2 differentiation characteristic of tumor cells can also be promoted by the microenvironment of the tumor. The non-malignant cellular infiltrate has a role in the pathomechanism: either in tumor initiation, progression, or in the selection and promotion of malignant cells, as well as in the development of the general immunosuppressive state characteristic of advanced stages. The paper discusses new knowledge on the pathogenesis of MF and SS, demonstrating new therapeutic options.