A case report on missed case of lynch syndrome with PMS2 loss of expression at extreme age.

Lynch syndrome is an autosomal dominant disorder affecting one of the mismatch repair (MMR) genes. Amsterdam and revised Bethesda criteria are used to identify individuals at risk for Lynch syndrome, but they have limited sensitivity. The CRC Risk assessment tool is effective in identifying high-risk individuals and mutation carriers of Lynch syndrome. Here, in this case report, we present an 84-year-old female with a positive family history of colon cancer in her mother and grandmother, presented in the clinic for a 3-year colonoscopy follow-up, who was found to have a 3 cm sigmoid lesion with central ulceration at 28 cm. The pathology of the sigmoid lesion revealed moderately to poorly differentiated invasive adenocarcinoma of the sigmoid colon. Immunohistochemistry testing for MMR proteins revealed a loss of nuclear expression of PMS2. She underwent a robotic total abdominal colectomy, and a robot-assisted laparoscopic hysterectomy in the same setting. This case offers valuable insight into the reasons behind the delayed diagnosis of lynch syndrome and suggests solutions to prevent such cases from being missed.