[Rectal Mucosa-associated Lymphoid Tissue Lymphoma Treated with Endoscopic Resection].

A primary extranodal B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) is a distinct clinical-pathological entity that develops in diverse anatomic locations. However, colorectal involvement is rare. The authors encountered a case of a MALT lymphoma of the rectum in a 69-year-old woman who complained of up to 3 kg weight loss during 3 months. A colonoscopy demonstrated a 1.0×1.0 cm sized subepithelial tumor (SET) at the lower rectum. The patient underwent an endoscopic mucosal resection with ligation for the SET. Pathological analysis revealed marked small to medium-sized lymphocytic infiltration. Immunohistochemistry revealed neoplastic cells positive for CD20 and bcl-2. A polymerase chain reaction detected immunoglobulin H gene rearrangement. Finally, rectal MALT lymphoma was diagnosed. Computed tomography and positron emission tomography scans showed that there was no lymph node metastasis or other organ involvement. A bone marrow biopsy was found to be negative for any neoplastic process. Therefore, the Ann Arbor stage was IeB. Helicobacter pylori (H. pylori) was not detected in the gastric biopsy specimens. Thus far, she has had no relapse since the endoscopic resection. The incidence of rectal MALT is very rare, and treatment is unclear. This paper reports a case of rectal MALT lymphoma treated successfully with only an endoscopic resection.