Introduction: The clinical presentation of two tumors in Lynch syndrome is rare, it however becomes exceptionally rare when three tumors are diagnosed. Indeed, only very few cases have been described.

Case Presentation: A 42-year-old male came into the emergency room complaining of a non-specific abdominal pain associated with nausea. The radiological and endoscopic evaluation revealed an intestinal subocclusion associated with a rectal and duodenal mass and a polyp originating from the ileocecal valve. The biopsies of the duodenal and rectal lesion resulted in a diagnosis of infiltrating adenocarcinoma of the duodenum and an adenocarcinoma of the middle rectum. Staging was completed and a molecular evaluation showed a heterozygous variant of MSH2 (InSiGHT class 5) compatible with Lynch Syndrome. The patient underwent an ileo-colic resection, a duodenocephalopancreatectomy and a resection of the rectum at three different times. The final diagnosis confirmed the duodenal and rectal neoplasia associated with a high-grade dysplasia on the polypoid lesion.
In consideration of the clinical history and diagnosis of Lynch syndrome, the patient was referred for a detailed oncology and genetic evaluation to agree upon the most appropriate oncological treatment and follow-up program.

Conclusions: Triple malignancy in a single patient is very unusual. Its management depends on the stage of the disease. Surgery is the standard of care in localized cancers.

Keywords: Intestinal invagination; Duodenal; Rectal; Neoplasia; Lynch syndrome