Mucosa-associated lymphoid tissue lymphoma with unusual 18F-FDG hypermetabolism arising at the colorectal anastomosis.

Mucosa-associated lymphoid tissue (MALT) lymphoma usually originates from the stomach and presents with low 18F-fluorodeoxyglucose (FDG) avidity with average maximum standard uptake value of 3.6. Colorectal MALT lymphoma is a rare entity that contributes to 1.6% of all MALT lymphomas and < 0.2% of large intestinal malignancies. The case reported herein firstly revealed stage IIE MALT lymphoma with unexpected higher 18F-FDG avidity of 18.9 arising at the colorectal anastomosis in a patient with a surgical history for sigmoid adenocarcinoma, which was strongly suspected as local recurrence before histopathological and immunohistochemical examinations. After accurate diagnosis, the patient received four cycles of standard R-CVP regimen (rituximab, cyclophosphamide, vincristine and prednisone), combined target therapy and chemotherapy, instead of radiotherapy recommended by National Comprehensive Cancer Network guidelines. He tolerated the treatment well and reached complete remission.