Primary Hepatic Neuroendocrine Carcinoma Treated with Doxorubicin and Cyclophosphamide in a Dog.

A 7 yr, 6 mo old male neutered Australian cattle dog cross presented to a referral hospital with a large abdominal mass. An abdominal ultrasound revealed multifocal lesions throughout the liver, which were suspicious for intrahepatic metastasis, with no evidence of extrahepatic metastatic disease. Cytology indicated neoplasia of epithelial origin, with neuroendocrine neoplasia the primary suspicion. The patient was started on a maximally tolerated chemotherapy protocol of doxorubicin and metronomic cyclophosphamide. Stable disease was found on repeat abdominal ultrasounds, and the patient tolerated the protocol well. On completion of five doxorubicin doses, the dog was continued on metronomic cyclophosphamide and meloxicam. Progressive hepatic disease was found at 10 mo. The patient was euthanized 15.5 mo (465 days) after commencing treatment. Histopathology and immunohistochemistry (synaptophysin) performed on liver collected postmortem indicated (primary) hepatic neuroendocrine carcinoma. Primary hepatic neuroendocrine carcinomas are rare in dogs, and there is no standard of care for treatment. To the authors' knowledge, this is the first report of a primary hepatic neuroendocrine carcinoma treated with high-dose doxorubicin and metronomic cyclophosphamide.