Adult T-cell Leukemia/Lymphoma (ATLL) is an aggressive neoplasm of T lymphocytes associated with Human T-lymphotropic virus type1 (HTLV-1) infection. HTLV-1 is a public health problem because it is endemic in native groups in Latin America, and its infection leads to several chronic diseases as ATLL. We aimed to review current literature of ATLL in order to consider it as a differential diagnosis in front of patients with compatible symptoms. Prognosis is still poor in aggressive and indolent variants, with survival rates from months to few years. Treatment based on chemotherapy, antiretroviral, and allogenic stem cell transplantation are currently improving survival rates, but with limited results.