Unusual Presentation of a Hepatic Neuroendocrine Tumor With Elevated CEA and CA 19-9: A Case Report.

Neuroendocrine tumors (NETs) of the gastrointestinal tract (GIT) are rare malignancies, which may have unique presentations. The diagnostic process predominantly relies on immunohistochemical analysis. While tumor markers are extensively utilized in diagnosing and monitoring GI malignancies, their specific role in NETs has not been fully explored. This case describes an 83-year-old male presenting with jaundice and general weakness. Diagnostic imaging through MRI and CT angiography (CTA) revealed a nodular texture on the liver's surface suggesting cirrhosis. The presence of elevated tumor markers, specifically carcinoembryonic antigen (CEA) and cancer antigen 19-9 (CA 19-9), raised suspicions of malignancy. A subsequent liver biopsy confirmed the diagnosis of small-cell high-grade neuroendocrine carcinoma accompanied by reactive fibrosis. As per our knowledge, this case is the first recorded instance of a liver neuroendocrine tumor (NET) exhibiting elevated levels of both CEA and CA 19-9, with no abnormalities detected in the gallbladder, biliary tree, and bowel in the MRI with magnetic resonance cholangiopancreatography (MRCP) and CTA. This is an atypical presentation of a liver NET, mimicking cirrhotic liver morphology, and underscores the potential diagnostic relevance of tumor markers CEA and CA 19-9 in such cases.