Primary, solitary, adult T-cell leukemia / lymphoma of the descending colon.

We herein report a patient with adult T-cell leukemia/lymphoma (ATLL) of the descending colon. A 64-year-old man was admitted to our hospital complaining of left lower abdominal pain. Endoscopic examination revealed an ulcerative tumor in the descending colon that was diagnosed as T-cell lymphoma by biopsy. Neither distant organ metastasis nor lymph node swelling was observed by radiographic examinations. Curative excision with left hemicolectomy and regional lymph node dissection was performed. Surgical sections contained ulcerative and superficially elevated lesions; these were continuous with each other. Histological examination revealed diffuse proliferation of medium-sized abnormal lymphoid cells. Immunohistochemically, these lymphoid cells were positive for UCHL-1/CD45RO and CD3 and negative for CD79a, indicating that the tumor was a primary malignant T-cell lymphoma of the descending colon. Integration of the proviral DNA of human T-lymphotropic virus type 1 (HTLV-1) was confirmed by Southern blotting analysis.