Metachronous Colorectal Carcinomas and Pancreatic Metastasis in Clinically Suspected Lynch Syndrome: An 18-Year Oncologic Course.

Lynch syndrome (LS) is an autosomal dominant hereditary cancer predisposition syndrome associated with colorectal and extracolonic malignancies. Metachronous colorectal carcinomas are well recognized, whereas pancreatic involvement by metastatic colorectal carcinoma is rare and diagnostically challenging. We report the case of a 58-year-old male patient with a strong family history of colorectal carcinoma and an 18-year history of multiple metachronous colorectal malignancies who developed a pancreatic body-tail mass during oncologic surveillance. Histology showed a high-grade malignant epithelial neoplasm with solid/nested architecture and extensive necrosis. Immunohistochemistry (IHC) demonstrated diffuse SATB2 positivity and loss of MLH1/PMS2 expression, with retained MSH2/MSH6. The findings favored metastatic colorectal carcinoma involving the pancreas in the setting of clinically suspected Lynch syndrome. This case emphasizes the importance of clinicopathologic correlation, cautious interpretation of MMR deficiency, and long-term multidisciplinary surveillance.