1364 Metastatic Pancreatic Adenocarcinoma Presenting as a Colonic Obstruction

Abstract

INTRODUCTION: Pancreatic cancer is the fourth most common cause of cancer-related mortality in the United States largely due to a delayed diagnosis at an advanced stage. Patients with pancreatic tumors commonly present with abdominal pain, anorexia and jaundice. Nearly 50% of patients with pancreatic cancer present with metastatic disease, most commonly to the liver. Rarely it can metastasize to the colon and present with an obstruction. CASE DESCRIPTION/METHODS: A 68-year-old male presented with a 2 week history of abdominal pain and constipation. On physical exam, the abdomen was distended with generalized tenderness. Initial computed tomography (CT) scan of the abdomen and pelvis showed abnormal colonic and small bowel distention with induration surrounding the proximal sigmoid colon and distal decompression. There was also evidence of a bulky mass-like appearance of the pancreatic tail and prominent pericolonic lymph nodes surrounding the sigmoid colon. Despite conservative measures, the patient had progressively worsening colonic distention on serial abdominal X-rays and a repeat CT scan was concerning for perforated viscus. The patient underwent emergent exploratory laparotomy and a large inflammatory mass was noted in the sigmoid colon. A subtotal colectomy with end ileostomy was performed. Surgical pathology revealed metastatic mucinous adenocarcinoma to the colonic wall (Figure 1). Several days later, an endoscopic ultrasound with fine needle aspiration was obtained and showing a 31 × 20 mm hypoechoic mass involving the body and tail of the pancreas (Figure 2). Pathology was positive for malignant cells consistent with adenocarcinoma. Histopathological patterns of both tumors were compared and had almost identical features. DISCUSSION: Differentiating a primary colonic cancer from metastasis can be challenging and the absence of mucosal involvement favor metastatic disease. In cases where metastasis are favored, immunohistochemistry is helpful to determine the primary origin of the tumor. It is not uncommon to encounter an extrapancreatic adenocarcinoma suspected to originate from the pancreas, with most common locations being liver, lymph nodes, lungs, and adrenal glands. Metastatic pancreatic cancer to the colon is extremely rare and no clear mechanism has been identified. Despite its rarity, pancreatic cancer should be considered in patients presenting with colonic obstruction and a pancreatic mass on imaging.