Primary mucosa-associated lymphoid tissue (MALT) lymphoma occurring in the rectum: a case report and review of the literature.

The primary extranodal B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) is a distinct clinical pathologic entity that develops in diverse anatomic locations such as the stomach, salivary gland, thyroid, lung, and breast; however, colorectal involvement is rare. To the best of our knowledge, only 30 cases of primary rectal MALT lymphoma have been published in the English language literature, mostly from Japan. A single case has been reported from the US before this report. The most common symptoms ranged from asymptomatic to occult or gross gastrointestinal bleeding. Simultaneous involvement of the cecum or colon was seen in 20% of the patients. Ninety percent of the patients were classified as low grade, Stage 1 at the time of diagnosis. Polypoid lesions were 10-fold more common than ulcerative lesions. Seven patients were reported to have H pylori in the stomach. The majority of the patients underwent surgical or endoscopic resection as a cure; however, controversy exists with regards to antibiotic treatment or observation alone because of unknown etiopathogenesis. Infection with microorganisms other than H pylori has been postulated in the development of rectal MALT lymphoma; however, this hypothesis remains unproven. The overall prognosis of rectal MALT lymphoma appears favorable; however, long-term follow-up data is lacking. Therefore, periodic clinical monitoring should be done in these patients.