Primary cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of lymphoproliferative disorders derived from “skin-homing” lymphocytes CD4+. This phenomenon is also observed in the course of other chronic inflammatory processes in the skin, which results in significant diagnostic difficulties in CTCL, especially in the early stages of the disease. Recent studies indicate the pathogenetic complexity of CTCL. It is believed that one of the most important factors leading to the clonal proliferation of lymphocytes in the skin is its microenvironment. It has been proved that not only CLA (cutaneous leucocyte antigen) but also numerous chemokines, their receptors (CCR4, CCR10, CCL17, CCL27) and cytokines (IL-15, IL-16, IL-17, IL-21, IL-22) are involved in the process of skin infiltration. In this article we present a systematic review of current opinions on the aetiopathogenesis of mycosis fungoides and Sézary syndrome, which accounts for 75% of all primary CTCL.