Multiple Colorectal Mucosa-Associated Lymphoid Tissue Lymphoma Successfully Treated with Chemotherapy

The standard treatment for colorectal mucosa-associated lymphoid tissue (MALT) lymphoma has not yet been established due to the rarity of the disease. Here, we report a case of long-term response to chemotherapy for colorectal MALT lymphoma (stage I). A 77-year-old frail female patient with diabetes mellitus and dementia developed melena of unknown etiology, and a colonoscopy was performed at a nearby hospital. A biopsy suggested malignant lymphoma, and she was referred to our department. As a result of re-examination of colonoscopy, a total of 3 submucosal tumor-like lesions were confirmed. Of these, a biopsy of the lesions in the ascending colon and rectum was performed, and MALT lymphoma was diagnosed on the basis of the histopathological findings. Following close examination, no other lymphoma lesions were found, and the patient was diagnosed with primary colorectal MALT lymphoma, stage I. After 1 course of R-THP-COP chemotherapy (rituximab + cyclophosphamide, pirarubicin, vincristine, and prednisone), the rectal lesion was confirmed to have almost disappeared endoscopically, and lymphoma cells were not found histopathologically. The patient was determined to be in complete remission (CR). However, due to hematological toxicity and a slight worsening of glucose control, the second chemotherapy course was changed to the BR regimen (rituximab + bendamustine), and 4 courses were performed (5 total courses of chemotherapy). Currently, >3 years have passed since reaching CR, and the patient is alive without recurrence.