S5513 When Diarrhea Isn’t Just Diarrhea: A Case of Metastatic pNET With Hemodynamic Collapse

Introduction: Pancreatic neuroendocrine tumors (pNETs) are rare malignancies, comprising less than 2% of all pancreatic neoplasms. When functional, they can produce a wide range of hormonal symptoms. However, non-functional pNETs often evade early detection, presenting only after extensive metastasis. We present a rare case of a metastatic pNET manifesting with severe diarrhea, hypotension, and multiorgan dysfunction—mimicking sepsis and gastrointestinal bleeding. Case Description/Methods: A 71-year-old man with a background of coronary artery disease, heart failure (EF 65%), chronic obstructive pulmonary disease, and ICD presented with progressive bilateral leg weakness, lethargy, and multiple episodes of bloody diarrhea. On admission, he was hypotensive (BP 81/71 mmHg), jaundiced, and in atrial flutter. Labs revealed leukocytosis, acute kidney injury, cholestatic liver pattern, and progressive thrombocytopenia. CT abdomen/pelvis showed multiple hepatic lesions concerning for metastasis. Tumor markers were notable for CA 19-9 of 421.6 U/mL and chromogranin A of 808 ng/mL. CEA and AFP were within normal limits. Stool studies, including C. difficile toxin, were negative. Due to persistent instability, endoscopic evaluation and biopsy were deferred. Clinical suspicion of a neuroendocrine tumor was made based on biomarker profile and imaging. Despite aggressive supportive measures, the patient developed multiorgan failure. He opted for comfort-focused care and passed away shortly after ICU transfer. Discussion: This case underscores the importance of considering NETs in patients with unexplained secretory diarrhea, liver lesions, and systemic deterioration. pNETs can remain clinically silent until advanced stages and may mimic more common pathologies like gastrointestinal bleeding or sepsis. Biomarkers such as chromogranin A can guide diagnosis when invasive procedures are contraindicated. Early recognition is essential to improve outcomes, though in advanced cases, therapeutic options may be limited.