A Single Colonic Polyp Having Both Tubular Adenoma and Mantle Cell Lymphoma: A Case Report.

Introduction: Mantle cell lymphoma (MCL) is a distinct subtype of B-cell non-Hodgkin lymphoma. MCL lymphoma can occur in the gastrointestinal tract (GIT) as a primary lymphoma; more commonly, the GIT can be secondarily involved. A colonic polyp simultaneously having MCL with overlying adenomatous changes is highly unusual, and few cases were reported. Herein, we describe a unique instance of a single adenomatous polyp in the left colon overlying a small lymphoid population proven to be MCL in a patient recently diagnosed with MCL. We believe this report will increase the awareness of pathologists and clinicians of such a unique and unusual clinical presentation. Case Presentation: A 53-year-old male patient presented with a history of generalized lymphadenopathy, bilateral pleural deposits, and splenomegaly. Axillary lymph node excisional biopsies were sent for pathology and reported MCL, diffuse pattern, classic variant. Three weeks later, the patient underwent upper and lower endoscopy for mild upper abdominal discomfort. Upper endoscopy showed mild gastropathy, and colonoscopy revealed a small polyp at the descending colon. Pathology of the colonic polyp showed a tubular adenoma with low-grade dysplasia overlying a well-circumscribed mucosal/submucosal nodular lymphoid aggregate. The lymphoid aggregate exhibited histological and immunohistochemical features of MCL. Thus, a diagnosis of tubular adenoma coexisting with MCL in the same polyp was made. Conclusion: Tubular adenoma with MCL is an exceedingly rare phenomenon with unclear pathogenesis. We report this case to highlight the importance of examining lymphoid tissue in adenomas and to increase the awareness among clinicians and pathologists of such a unique presentation.