Two Cases Of Primary Mucosa-Associated Lymphoid Tissue (Malt) Lymphoma Occurring In The Rectum Treated With Endoscopic Resection And Antibiotic Therapy: A Report From The United States

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 stomach, salivary gland, lung, and breast; however, primary colorectal involvement is rare. This is the first report of primary MALT lymphoma occurring in the rectum from the USA. CASE 1: A 57-year-old white woman was found to have a sessile, 1.5 to 2 cm, nodular rectal mass on screening colonoscopy. The rectal mass appeared limited to the mucosa on endoscopic ultrasound and it was removed endoscopically. The immunohistochemistry with B-cell marker (CD 20) demonstrated predominantly B cells and lymphoepithelial lesions, whereas T cells (CD3) were few in the lymphoid aggregate. These features confirmed MALT lymphoma; however, H pylori was not seen. Her clinical stage (Ann Arbor) was 1AE. She was treated with H pylori eradication therapy. She continues to remain cured at 1 year of follow-up. CASE 2: A 69-year-old Hispanic man underwent screening colonoscopy that revealed 3 sessile rectal polyps and 1 cecal polyp, each measuring approximately 7-8 mm. All polyps were removed using cold snare. Histology showed typical features of low grade MALT-lymphoma; however, H pylori was not seen. His clinical stage (Ann Arbor) was 1AE. He was also treated with antibiotics. After 1 year of follow-up his colonoscopy showed a 10 mm submucosal rectal nodule near the dentate line. Surgical excision was recommended; however, patient was lost to follow-up. Discussion: Only 20 cases of primary rectal MALT are published in the English language literature, mostly from Japan. The commonest presenting symptoms ranged from asymptomatic to occult or gross gastrointestinal bleeding. Simultaneous involvement of the cecum was seen in one patient. All except one patient were low grade, stage 1 at the time of diagnosis. Polypoid lesions were 10-fold commoner than ulcerative lesions. Only one patient was reported H pylori positive. Majority of patients underwent surgical or endoscopic resection as a cure. However, controversy exists with regards to antibiotic treatment or observation 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 prognosis appears favorable; however, the long-term follow-up data is lacking. Therefore, periodic clinical monitoring should be done.