Resolution of Recurrent Severe Hypoglycemia After Surgical Excision of a Primary Hepatic Neoplasm of Uncertain Histogenesis in a Dog: A Case Report

Primary hepatic neoplasms in dogs, while uncommon, are occasionally associated with severe hypoglycemia, although the underlying mechanism may be difficult to establish. A 7-year-old castrated male Maltese dog weighing 3.6 kg was referred for recurrent bilateral pelvic limb weakness, episodic collapse, and abdominal distension. Severe hypoglycemia was documented, with a blood glucose concentration of 26 mg/dL. Computed tomography revealed a large mass arising from the right lateral liver lobe, with no identifiable pancreatic mass or distant metastasis. The serum insulin concentration measured during hypoglycemia was low at 1.0 μU/mL, making insulinoma less likely. Glycemic control temporarily or partially improved during prednisolone treatment; however, severe hypoglycemia recurred after prednisolone discontinuation before surgery. The hepatic mass was surgically excised. Dextrose-containing intravenous fluids were maintained for 6 h postoperatively, and no recurrent clinically significant hypoglycemia was documented after their discontinuation. Histopathologic examination revealed a poorly differentiated neoplasm with mesenchymal morphology, occasional cytoplasmic vacuolation, and no unequivocal lipoblasts. The neoplastic cells showed diffuse vimentin immunoreactivity, weak cytoplasmic S-100 immunoreactivity in a subset of cells, and no immunoreactivity for smooth-muscle actin or hepatocyte paraffin 1. These findings raised the possibility of adipocytic differentiation but were insufficient to establish a specific tumor lineage; therefore, the lesion was classified as a primary hepatic neoplasm of uncertain histogenesis. At 247 days after surgery, the dog remained normoglycemic without supplemental glucose or glucocorticoid treatment, and no imaging evidence of local recurrence or distant metastasis was identified. The postoperative course supported an association between the hepatic neoplasm and hypoinsulinemic hypoglycemia. Non-islet-cell tumor hypoglycemia was suspected but remained unconfirmed because an insulin-like growth factor-mediated mechanism was not demonstrated.