An Unusual Presentation of Occult Small-Cell Neuroendocrine Carcinoma as Acalculous Cholecystitis With Widespread Liver Metastasis

Small-cell neuroendocrine carcinoma, often classified as small-cell lung carcinoma (SCLC) type, is an aggressive neuroendocrine tumor with early metastatic potential that can lead to unexpected patient presentations. We report the case of a 69-year-old man who presented to the emergency department with worsening right upper abdominal pain, nausea, and vomiting for the past several days. The clinical picture and the workup, including the complete metabolic panel and complete blood count, were highly suggestive of acute cholecystitis with transaminitis and direct hyperbilirubinemia. The ultrasound and magnetic resonance cholangiopancreatography of the abdomen revealed a diffusely hyperdense and hypertrophic liver without evidence of choledocholithiasis. After initial resuscitation, the patient underwent laparoscopic cholecystectomy. Intraoperative findings were consistent with diffuse miliary liver metastatic disease of unknown etiology, rigid liver parenchyma, an extremely frail gallbladder wall, and mild ascites. A biopsy of the liver and cholecystectomy were performed. The final pathology revealed metastatic SCLC to the liver and widespread intravascular tumor emboli, causing diffuse ischemia of the entire gallbladder wall. The patient’s postoperative course was marked by the development of foudroyant liver insufficiency and worsening severe type B lactic acidosis.