A CASE OF MUCOSA ASSOCIATED LYMPHOID TISSUE LYMPHOMA IN THE COLON

Abstract

We report a case of mucosa-associated lymphoid tissue (MALT) lymphoma which was difficult to differentiate from early colon-cancer. The patient was a 72-year-old man who complained of abdominal pain, diarrhea and body weight loss (6kg in three years). Colonoscopy revealed a flat elevated lesion in the sigmoid-colon. The lesion was 10 x 10mm in diameter and had a shallow depression and bleeding. It's margin was unclear and had no bridging fold. The histological study of the biopsy specimens revealed a simple chronic colitis. However, from the colonoscopic findings, we highly suspected early colon cancer. Endoscopic mucosal resection was performed for diagnostic purposes. The histological study of resected specimen revealed formation of lymph follicles and infiltration of small or medium sized lymphocytes with cleaved nuclei in the lamina propria and submucosa. Invasion of abnormal lymphocytes into epithelium, so called lymphoepitherial lesion, were observed and abnormal lymphocytes different from plasma cells were present in the lamina propria. The abnormal lymphocytes were positive for L-26 and negative for UCHL-1 in immunological study. The patient was diagnosed as MALT lymphoma and the depth of invasion was deep submucosal layer (sm3). Because abdominal ultrasonic examination and Ga scintigram showed no abnormality, the patient underwent a recto-sigmoidectomy for curative therapy. A similar lesion with invasion in the deep submucosal layer was found in another part of sigmoid colon. This is a rare case showing the early stage of colon MALT lymphoma. Endoscopy should be performed carefully to differentiate early stage of malignant lymphoma from early colon cancer.