Cutaneous T-cell lymphomas are a heterogenous group of T lymphoid proliferative disorders that arise and predominate in the skin. Mycosis fungoides and Sezary syndrome are the most frequent cutaneous T cell lymphomas, and their frequency is increasing. The course is indolent in early stages and much more aggressive in late stages. Major advances have been made in the pathophysiology of these rare diseases. Many new treatments are currently being evaluated, and it is important to test them in prospective controlled collaborative studies. New biomarkers have been reported, leading to the development of new targeted monoclonal antibodies that specifically destroy tumor T lymphocytes and spare reactive T lymphocytes.