A case of metachronous ascending colon cancer and synchronous primary rectal and duodenal cancer in a patient with Lynch syndrome

Multiple primary malignant tumours (MPMTs) are defined as the simultaneous or sequential occurrence of two or more primary malignant tumours in a single patient, which may originate from the same organ, paired organs, different parts of the same system, or different organs. Synchronous MPMTs develop within 6 months of the primary tumour, while metachronous ones occur more than 6 months later. The available sources have no information on metachronous or synchronous colorectal and duodenal cancer. Objective — to present treatment outcomes of a rare case of metachronous ascending colon cancer and synchronous primary rectal and duodenal cancer in a patient with Lynch syndrome. A male patient, born in 1963, underwent a right‑sided hemicolectomy for ascending colon mucinous adenocarcinoma — stage III (рT4рN1M0) — in 2002. In the summer of 2022, he complained of pain in the right hypochondrium, nausea, general weakness, and blood in the stool. The examination revealed the presence of synchronous primary cancer in the rectosigmoid section and duodenal cancer. The decision to proceed with a two‑stage surgical intervention was based on the partial colonic obstruction. The first stage (September 08, 2022) included the anterior resection of the rectum with sigmo‑recto anastomosis (рТ4сN2bM0, stage III, R‑0). The second stage (December 08, 2022) included the resection of a portion of the descending and lower horizontal parts of the duodenum with duodeno‑duodenoanastomosis, followed by Roux‑en‑Y gastrojejunostomy. The procedure entailed stitching the stomach in the prepyloric section, performing a cholecystectomy, and draining the abdominal cavity (duodenal adenocarcinoma with free margins: R‑0). The patient was diagnosed with Lynch syndrome based on immunohistochemistry screening results and genetic studies. After the first and second stages, the patient categorically refused to undergo a course of traditional adjuvant therapy. At the control CT scan 1.9 months after the last operation, there were no signs of prolongatio morbi. A rare case of synchronous rectal and duodenal cancer, demonstrating favourable treatment outcomes after two‑stage surgery without standard adjuvant therapy, is described. Patient follow‑up is ongoing; therefore, the results may change in the future.