Synchronous colonic mucosa-associated lymphoid tissue lymphoma found after surgery for adenocarcinoma: A case report and review of literature

BACKGROUND Mucosa-associated lymphoid tissue (MALT) lymphoma is a subtype of non-Hodgkin lymphoma that is mainly involved in the gastrointestinal tract. The synchronous occurrence of colonic MALT lymphoma and adenocarcinoma in the same patient is extremely rare. We here report a case of synchronous colonic MALT lymphoma found on surveillance colonoscopy five months after surgery and chemotherapy for sigmoid adenocarcinoma. CASE SUMMARY A 67-year-old man was admitted because of hematochezia for two months. Colonoscopy suggested a colonic tumor before hospitalization. Abdominal computed tomography (CT) revealed local thickening of the sigmoid colon. The patient underwent a left hemicolectomy with local lymph node dissection. The histopathology revealed moderately differentiated adenocarcinoma and partially mucinous adenocarcinoma. The pTNM stage was T3N1Mx. The patient received chemotherapy with six cycles of mFOLFOX6 after surgery. Colonoscopy was performed five months later and revealed single, flat, polypoid lesions of the colon 33 cm away from the anus. Subsequently, the patient underwent endoscopic mucosal resection for further diagnosis. The pathological diagnosis was MALT lymphoma. Positron emission tomography /CT suggested metastasis. The patient refused further treatment and died ten months later. CONCLUSION Colonic MALT lymphoma may occur after surgery and chemotherapy for adenocarcinoma as a synchronous malignancy. Regular surveillance colonoscopy and careful monitoring after surgery are critical.