We encountered two cases of adult T cell leukemia (ATL) associated with a cancer of other organs. In both cases, atypical lymphocytes were found in the peripheral blood, with the anti HTLV-1 antibody test being positive. Careful examination revealed that these cases were smoldering ATL.
One case had bloody stool. Barium enema and fiberoptic colonoscopy resulted in a diagnosis of carcinoma of the anal canal, and abdominoperineal excision of rectum was performed.
In the other case, a mass was palpated in the right side of the neck, and with a diagnosis of submandibular carcinoma based on cervical CT scan and echography, the mass was resected.
In cases of ATL, compromised immunocompetence seems to be included in the mechanisms of development of multiple cancer, where a probable high risk of gastrointestinal carcinoma is considered. Since ATL associating with multiple cancer poses many therapeutic problems and the authors also have had troubles in the treatment, these cases are reported for reference.