Metastatic pancreatic cancer with multiple metastases confined to the large intestine: a case report and literature review

The incidence and mortality rate of pancreatic cancer are increasing worldwide. Regional lymph nodes, liver, lung, and peritoneum are common sites of metastasis from pancreatic cancer, but the gastrointestinal tract is rare as a metastatic organ from pancreatic cancer. An 80-year-old man was referred to our department for a hypovascular pancreatic mass on contrast-enhanced computed tomography (CECT). Endoscopic ultrasound-guided fine needle aspiration revealed adenocarcinoma, and he was diagnosed with pancreatic cancer. No lymph nodes or distant metastases were detected by either CECT or gadolinium-enhanced magnetic resonance imaging, and we evaluated this case as borderline resectable. However, total colonoscopy for positive fecal occult blood tests revealed a reddish and hemorrhagic mucosal thickening in the ascending and sigmoid colon and rectum, which was inconsistent with primary colorectal cancer. Biopsy specimens from these sites revealed cytokeratin (CK)7-positive and CK20- and CDX2-negative adenocarcinoma, consistent with cancer of pancreatic origin. The patient underwent palliative chemotherapy with gemcitabine but died from COVID-19 infection eight months after diagnosis. Performing total colonoscopy as a preoperative screening is important for accurate cancer staging of patients with possible resectable pancreatic cancer.