Collision Tumor Consisting of Mantle Cell Lymphoma and Mucinous Adenocarcinoma in Ascending Colon: Case Report

<b>Introduction:</b> Mixed neoplasms represent a big family of complex tumors that consist of more than one neoplastic tissue. Mixed tumors are categorized into collision, composite, carcinosarcomas, and amphicrine tumors. Case Report: Hereinafter, we describe a case of a collision tumor composed of mantle cell lymphoma and mucinous adenocarcinoma located in the ascending colon in a 63-year-old man. A patient was admitted to the hospital due to sideropenic anemia, central abdominal pain spreading into the right lumbal area, and occasional loose stools. <b>Results:</b> Laboratory tests revealed sideropenic anemia, thrombo-cytosis, and inflammatory syndrome. A colonoscopy detected an ulcer-proliferative mass located at the hepatic flexure. Endoscopic biopsy from the mass confirmed poorly differentiated adenocarcinoma. A computed tomographic scan demonstrated a circumferential thickening of the hepatic flexure that narrows the colon lumen to the length of 10 cm. Multiple regional lymph nodes were enlarged. Consequently, the patient underwent a right hemicolectomy with ileotransverse colon anastomosis. Pathologic findings showed an ulcer-exophytic mass in ascedens. Microscopic examination of the lesion detected a poorly differentiated mucinous adenocarcinoma colliding with mantle cell lymphoma that was confirmed by immunohistochemistry. Regional lymph nodes were enlarged, involved by lymphoma. Following the surgery, the patient received R-CHOP chemotherapy. To the best of our knowledge, only four such cases have been reported in the literature so far. Unfortunately, long-term follow-up was not available. <b>Conclusions:</b> The diagnosis of collision tumors can be very challenging, and prognosis and therapy are still not investigated enough. More reports of collision tumors should be documented to establish standard protocols for treatment.