We present the possibilities of diagnosis correlating the pathological, immunophenotyping and clinical aspects of a rare case of T-cell lymphoma in a 23-year-old patient with leukemic transformation. In our consideration, it is very important to describe this case because in the literature there are very few cases presented and the treatment of this type of lymphoma does not present optimal results, the evolution of the patients being from three months to two years. The treatment modality that gives the possibility to prolong survival and cure is hematopoietic stem cell transplantation.