Introduction. Mycosis Fungoides (MF) is a primary epidermotropic T-cell lymphoma characterized by clonal proliferation of small and medium-sized T-lymphocytes with cerebriform nuclei. MF accounts for ≥ 50 % of all cutaneous lymphomas.The purpose of the study - description of a rare clinical observation of the debut of the development of Mycosis Fungoides in a patient in adolescence.Materials and methods. To verify the diagnosis, pathomorphological and immunohistochemical examination of a skin biopsy from the most infiltrated tumor-like lesion was used. The patient, born in 1978, turned to the clinic of Ural Research Institute of Dermatovenerology and Immunopathology with complaints of rashes on the skin of the trunk, accompanied by itching and soreness. Patient had been ill since the age of 16, when he first noticed the appearance of red spots on the skin of the chest without subjective sensations. In the last year he noted a significant deterioration of the disease: an increase in the number of spots, an increase in the intensity of itching, the appearance of tumor-like elements on the skin of the buttocks. In December 2022, he visited a dermatovenerologist and, in order to clarify the diagnosis, was sent to the Ural Research Institute of Dermatovenerology and Immunopathology.Discussion. The etiopathogenesis of the disease and the analysis of the few literature sources on the topic allows us to see the difficulty in early diagnosis and diagnosis in patients with early clinical manifestations of GM.Results. This clinical case demonstrates the possibility of the debut of GM in adolescence, the complexity of diagnosis in the early stages of development.Conclusion. The clinical case demonstrates the debut of GM in adolescence, emphasizes the need for clinical oncological alertness among dermatovenerologists.