Unusual Metastatic Pattern of Canine Insulinoma: Pulmonary and Skeletal Muscle Involvement

Although exocrine or endocrine pancreatic tumors are rare in dogs, canine insulinomas are highly metastatic. This case report describes a rare in-stance of insulinoma metastasis to the lungs and muscles rather than to com-mon metastatic sites such as the liver and pancreatic lymph nodes, making it a unique presentation in veterinary oncology. A 12-year-old spayed female Japa-nese Spitz was referred for the evaluation of recurrent hypoglycemic episodes characterized by lethargy, weakness, and seizures. The initial diagnostic workup, including blood glucose measurements, confirmed severe hypoglycemia, which prompted further diagnostic imaging. Computed tomography (CT) identified additional lesions in the right caudal lung lobe, right sartorius, and left serratus muscle, suggesting widespread metastatic lesions. Based on imaging and laboratory examinations, surgical excision of the multiple lesions was performed. The procedure included a left pancreatectomy, right caudal lung lobectomy, excision of the affected portion of the sartorius muscle, and splenectomy. Histopatholog-ical examination of the pancreatic tumor confirmed the diagnosis of islet cell car-cinoma. The resected pulmonary and sartorius muscle masses were diagnosed as metastatic carcinoma. Follow-up CT revealed an additional liver lesion and an increased nodule size in the serratus muscle. This is the first reported case of canine insulinoma with metastasis to the lungs and multiple skeletal muscles, making it a unique presentation in veterinary oncology. In conclusion, the present case suggests that insulinoma metastasis should be included in the differential diagnosis when muscular or pulmonary lesions are observed in dogs diagnosed with insulinoma.