Multiple Lymphomatous Polyposis Associated With Mucosa-Associated Lymphoid Tissue Lymphoma of the Colon

CASE REPORT

A 64-year-old man visited our department with tarry stools and anemia. Physical examination revealed no lymphadenopathy. Laboratory testing showed anemia (serum hemoglobin 6.4 g/dL). Esophagogastroduodenoscopy revealed no abnormalities. Computed tomography revealed numerous enlarged mesenteric lymph nodes, and the patient underwent colonoscopy that revealed multiple polypoid lesions throughout the colon. The polypoid lesions varied in size from 0.5 to 1 cm and were flat with a central depression (Figure 1). Some lesions showed a submucosal tumor-like ridge, magnifying endoscopy with narrow-band imaging revealed vasodilation on the surface of the nodules (Figure 2). Histopathological examination of multiple biopsy specimens revealed lymphoepithelial lesions with diffuse proliferation of atypical lymphocytes, which on immunohistochemical examination showed immunopositivity for CD20 and CD79a, but immunonegativity for CD10 and cyclin D1 (Figure 3). In addition, the Ki-67 labeling index was 5% to 10%. These findings were compatible with low-grade B-cell mucosa-associated lymphoid tissue (MALT) lymphoma. The patient was transferred to another hospital for chemotherapy.

Figure 1.

Colonoscopy showing polypoid lesions varied in size from 0.5 to 1 cm and were flat with a central depression.

Figure 2.

Colonoscopy showing some lesions showed a submucosal tumor-like ridge, magnifying endoscopy with narrow-band imaging revealed vasodilation on the surface of the nodules.

Figure 3.

Histopathological examination of multiple biopsy specimens showing (A) lymphoepithelial lesions with diffuse proliferation of atypical lymphocytes (hematoxylin and eosin stain, 40× magnification) and (B) immunopositivity for CD20 (hematoxylin and eosin stain, 10× magnification).

As reported earlier by Freeman et al, about 35% of extranodal involvement takes place in the gastrointestinal system, mostly in the stomach followed by the small intestine and to a lesser extent the colorectal area (less than 6%).¹ Multiple lymphomatous polyposis is considered to be a rare condition and is believed to be the digestive counterpart to mantle cell lymphoma due to similarities found in the pathological and histological features of both conditions.^2–4 MALT lymphoma is often confused with mantle cell lymphoma because of their histologic similarities. A MALT lymphoma usually presents as a single lesion, whereas mantle cell lymphoma presents as multiple lymphomatous polyposis in the gastrointestinal tract. Immunohistochemically, these 2 types can be differentiated by the cyclin D1 status because MALT lymphomas and mantle cell lymphomas are immunonegative and immunopositive for cyclin D1, respectively. Because of the lack of an accepted etiology and a limited number of cases, no guideline has been issued for the treatment of colonic MALT lymphomas. Locally extended low-grade MALT lymphomas are currently treated with endoscopic or surgical excision, whereas high-grade MALT lymphomas and MALT lymphomas with multiple organ involvement may be treated using different modalities such as surgery, radiotherapy, chemotherapy, and, more recently, rituximab therapy. The optimal strategy should be determined based on the involved site, histologic type, and clinical stage in each patient.

DISCLOSURES

Author contributions: N. Nishimoto wrote the paper. Y. Sakakibara, S. Nakazuru, and K. Mori revised the manuscript for intellectual content. E. Mita approved the final manuscript and is the article guarantor.

Financial disclosure: None to report.

Informed consent was obtained for this case report.