A 14-year-old male castrated Pomeranian presented to the Cornell University Hospital for Animals (CUHA) Emergency Service for evaluation of an extensive cranial abdominal mass that was diagnosed radiographically by the referring veterinarian. This diagnosis was made following a 2 week history of inappetance, lethargy, vomiting, and intermittent dianhea. The mass was estimated to occupy 60 percent of the abdominal cavity based on radiographs. Computed tomography confirmed the presence of a mass comprising the entire quadrate liver lobe. A ventral midline laparotomy with quadrate liver lobectomy was performed, leaving an approximately 2 cm stalk of the mass behind. The patient recovered uneventfully from surgery with resolution of clinical signs. He was discharged to the care of his owners 2 days postoperatively. Histopathology confirmed that the mass was a poorly differentiated hepatocellular carcinoma displaying cellular atypia and bizarre neoplastic cells with nearly complete effacement of normal hepatic parenchyma. While several prognostic indicators regarding hepatocellular carcinoma have been documented, the presence of poor prognostic factors does not negate the potential benefits of surgical excision.