Synchronous adenocarcinoma of the endometrium and colon in a woman with Lynch syndrome associated with a mutation of the MSH6 gene.

[INTRODUCTION] Lynch syndrome (LS) is an autosomal dominant genetic condition, accounting for an estimated prevalence of 2-3% of the causes of hereditary colorectal carcinoma. In addition, it increases the risk of endometrial and ovarian cancer, among others.

[CASE REPORT] A 56-year-old woman with a 6-month history of pelvic pain, dyspareunia and hypermenorrhoea. Family history: her mother died of endometrial cancer at the age of 71, and her younger brother died of gastric cancer at the age of 61. A transvaginal ultrasound revealed a 20mm thickening of the endometrium, and the biopsy showed a FIGO 2 endometrioid carcinoma. Abdominal MRI demonstrated diffuse thickening of the rectum, while colonoscopy revealed an infiltrative, ulcerated tumour lesion in the sigmoid colon and a lesion in the rectum, consistent with invasive adenocarcinoma of the colon and adenoma with high-grade dysplasia in the rectal biopsy. Simultaneous surgical resection was indicated. A molecular panel confirmed a mutation in the MSH6 gene, confirming Lynch syndrome.

[CONCLUSIONS] A rare case of Lynch syndrome associated with an MSH6 gene mutation, diagnosed with synchronous endometrial carcinoma and adenocarcinoma of the sigmoid colon.