3174 Carcinoid Metastasis With Unknown Primary Tumor Origin

Abstract

INTRODUCTION: Carcinoid tumors are rare, slow-growing neuroendocrine tumors found throughout the gastrointestinal system. However, in 3% of cases, the primary tumor is never found. Because establishing the diagnosis and primary tumor location can be challenging, we present the case of an incidentally found metastatic carcinoid tumor to the liver without an identifiable primary. CASE DESCRIPTION/METHODS: A 60-year-old male presented to the Emergency Department with nausea, vomiting, vague abdominal pain, and profuse, cyclic diarrhea. RUQ US showed gallstones, hence he underwent cholecystectomy for presumed symptomatic cholelithiasis. During the procedure, a right focally hemorrhagic hepatic nodule lateral to the gallbladder was noted and completely resected. Pathology revealed a well-differentiated neuroendocrine tumor concerning for carcinoid metastasis. Subsequent CT Abdomen/Pelvis with Contrast was unremarkable except for ascending sigmoid colitis and diverticulosis. OctreoScan revealed two questionable foci in the right hepatic lobe and focal uptake in the proximal duodenum. This was concerning for possible origin, and the patient underwent an EGD, which did not reveal anything suspicious. Concomitant biopsies were also negative. In light of his ongoing vague abdominal pain and diarrhea, he underwent a colonoscopy that noted no obvious colonic carcinoid. Biopsies were consistent with chronic colitis. He was prescribed Lialda with improvement in diarrhea. At follow-up, his Chromogranin A was elevated at 1030 ng/mL; ESR and CRP were elevated at 37 mm and 0.8 mg/dL, respectively. Next, he underwent PET DOTATATE, which found hyperactivity in the right and left hepatic lobes and a focus in the mid-sternum compatible with osseous metastasis. Further investigation with MR Enterography revealed extensive, chronic diverticulitis with a colovesical fistula, an intramural sigmoid abscess, and two sites highly suspicious for liver metastasis. Despite these diagnostic modalities, primary tumor location has still not been found. As the patient remained asymptomatic, observation without medical intervention was recommended. DISCUSSION: Metastatic carcinoid tumors of unknown origin are ultimately diagnoses of exclusion after an extensive workup. Early diagnosis is imperative to survival. Therefore, familiarity with the clinical signs, symptoms, and diagnostic modalities of carcinoid syndrome may expedite early detection and diagnosis and improve overall prognosis.