Collision tumor of colonic adenocarcinoma and EBV-driven large B-cell lymphoma: A case report and review of literature

IntroductionCollision tumors of adenocarcinoma and lymphoma in the gastrointestinal tract are especially rare with few reported cases in literature. We report a unique case of a collision tumor and perform a literature review.Presentation of caseAn 86-year-old patient with a history of rheumatoid arthritis on chronic azathioprine and prednisone was found to have an invasive adenocarcinoma in the descending colon. A large atypical lymphocytic infiltrate was found at the base of this lesion, which demonstrated CD20, lambda and EBER positivity consistent with adenocarcinoma colliding with EBV-driven and lambda-restricted large B-cell lymphoma.DiscussionWith this report, there are now fifteen cases of this type of collision tumor although the true incidence may be higher. Our case is unique among previous reports as the collision developed within the setting of iatrogenic immunosuppression and tumor EBV positivity was demonstrated. The pathogenesis is unknown, and diagnosis requires a high-degree of suspicion.ConclusionIt is important to consider immunosuppression in a patient with adenocarcinoma, as presence of atypical lymphoid cells may be indicative of lymphoma.