S4075 Metastatic Adenocarcinoma Manifesting as Sub-Centimeter Colonic Polyps

Introduction: Subcentimeter colon polyps are a common finding typically deemed benign and often representing hyperplastic or diminutive adenomatous lesions with low malignant potential. This case highlights a rare occurrence of metastatic adenocarcinoma manifesting as sub-centimeter colonic polyps. Case Description/Methods: A 75-year-old lady presented with abdominal pain, bloating, early satiety, ribbon-like stools and 35 lb weight loss. Examination revealed diffuse mild abdominal tenderness. Initial labs were remarkable for anemia (Hgb 10.4 g/dL) with iron studies suggesting anemia of chronic disease, elevated creatinine 3.3 mg/dL (baseline normal) and elevated alkaline phosphatase 616 IU/L (remainder of liver function tests (LFTs) normal at presentation). Computed topography (CT) revealed ascites, mesenteric edema, cholelithiasis and sclerotic bone lesions concerning for metastases. Elevated CEA (562 ng/mL), CA 125 (291 U/mL), borderline CA 19-9 (45 U/mL) and normal AFP were noted. Endoscopic evaluation with esophagogastroduodenoscopy was unremarkable. Colonoscopy revealed no malignant appearing masses but multiple polyps were resected- a 10 mm polyp in ascending colon, 2 sub-centimeter polyps in the descending colon and one other 12 mm polyp. Pathology showed signet ring adenocarcinoma in all specimens, suggesting metastatic implants rather than colorectal primary. Bone marrow biopsy and ascitic fluid cytology revealed signet cells with immunophenotype suggestive of upper GI or pancreaticobiliary primary. Magnetic resonance cholangiopancreatography showed moderate intra and extrahepatic biliary dilation. CBD was 12 mm with a long stricture in the pancreatic head portion. Additionally, a hydropic gallbladder with multiple gallstones was noted. Given slowly worsening hyperbilirubinemia (4.3 mg/dL) and cholestatic LFTs. Endoscopic retrograde cholangiopancreatography was initially planned but was not pursued given change in goals of care to focus on comfort. Ultimately, patient’s hospital course was complicated by extensive deep vein thrombosis, urinary tract infections, and failure to thrive, and she passed away. Discussion: Metastatic implants from signet ring adenocarcinoma manifesting as sub-centimeter colonic polyps are extremely rare and presents a significant diagnostic challenge. Although such small polyps are typically considered benign based on endoscopic appearance alone, this patient’s presentation highlights that size should be considered, along with other suspicious clinical signs and symptoms. This presentation demonstrates the importance of utilizing all aspects of testing from clinical, radiologic, and endoscopic picture to assess polyp significance.