Synchronous colon cancer after treatment for rectal follicular lymphoma: A case report.

Colorectal follicular lymphoma (FL) is rare. In addition, it is even rarer that colon cancer develops synchronously with colorectal lymphoma. The present study reports a case of sigmoid colon cancer that developed 6 months after endoscopic resection of rectal FL. A 71-year-old man with a history of developing mucosa-associated lymphoid tissue lymphoma in his stomach at age 48, right neck region at age 59 (the latter later modified as FL) and lung adenocarcinoma at age 60 now suffers from rectal FL. Endoscopic submucosal dissection (ESD) was performed at our hospital (Aiiku Hospital), and 6 months after the treatment, sigmoid colon cancer was confirmed by colonoscopy for the follow-up study. The patient was successfully curatively resected by ESD plus local resection and has survived without a recurrence for >3 years with no treatment. It was speculated that in the present case, cancer-related genes were changed as a carcinogenic mechanism due to decreased immune function associated with the onset of lymphoma.