Introduction and importance The association of colonic adenocarcinoma with lymphoma is a rare entity. The purpose of our presentation is to draw the attention of the endoscopist, and the surgeon, to the need to remove any suspicious lesions in the exploration for colorectal cancer. The pathologist should be warned about this association in the face of any unusual change in the lymphatic environment around an adenocarcinoma. In the slightest doubt, an immunohistochemistry (IHC) should be performed in order not to ignore this association. Case presentation A 77-year-old patient, who had adenocarcinoma of the right colic flexure, in whom a chance discovery of lymphoma was made intraoperatively. This combination was treated with chemotherapy targeting adenocarcinoma classified as pT4N1M0, ahead of the low-grade lymphoma malignancy. After two years, the patient presented with a recurrence as left lateral cervical lymphadenopathy and died in a picture of generalized paralysis. Clinical discussion Digestive lymphoma associated with adneocarcinoma is defined according to strict criteria according to DAWSON. It always precedes adenocarcinoma because it disrupts the subject's immunocompetence. His diagnosis is suspected when the lymphatic environment around the adenocarcinoma is disturbed. The confirmation is assured with the IHC. Treatment should target the most aggressive cancer. Conclusion The synchronous colonic occurrence of a MALT-type lymphoma and an adenocarcinoma is rare but possible. The pathologist must be alert to its existence. Treatment depends on the tumor stage of the adenocarcinoma but also on the lymphoma and its grade and any therapeutic decision should only be made in a multidisciplinary meeting.