Coexistence of Primary Colorectal Cancer and Multiple Colonic Metastases from Pancreatic Tail Cancer: A Case Report

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INTRODUCTION: Colonic metastasis from pancreatic cancer is extremely rare. Distinguishing metastatic pancreatic cancer from primary colorectal cancer is clinically important because the therapeutic strategies differ substantially. We report an exceptionally rare case of pancreatic tail cancer with multiple colonic metastases coexisting with primary colorectal cancer. CASE PRESENTATION: An 83-year-old man presented with right lower abdominal pain, constipation, and weight loss. Four years earlier, MRI and magnetic resonance cholangiopancreatography (MRCP) had demonstrated a cystic lesion in the pancreatic tail. On admission, contrast-enhanced CT revealed a pancreatic tail tumor with suspected invasion of adjacent organs, lesions in the ascending and sigmoid colon, para-aortic lymph node metastasis, and peritoneal dissemination. Barium enema and colonoscopy showed stenotic lesions, and bowel obstruction developed. Palliative open right hemicolectomy and sigmoid colectomy were therefore performed. Gross examination revealed a mucosa-based type 2 lesion in the ascending colon and separate serosa-predominant lesions in the ascending and sigmoid colon. Histopathological and immunohistochemical analyses showed that the type 2 lesion represented primary colorectal cancer, whereas the other colonic lesions and peritoneal nodules were metastatic pancreatic cancer. The patient developed postoperative ileus and pneumonia, was discharged on POD 24, and died 6 months after surgery. CONCLUSIONS: Colonic metastasis from pancreatic cancer may sometimes be difficult to distinguish from primary colorectal cancer. In patients with pancreatic cancer, colonic lesions with relatively preserved mucosa and predominant serosal involvement should be considered in the differential diagnosis of metastatic disease. Markedly elevated carbohydrate antigen 19-9 levels may also provide an additional clue to pancreatic origin, although they are not diagnostic. Careful integrated assessment of the clinical course, imaging, and pathological findings is essential for accurate diagnosis and appropriate management.

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