Abstract
A four-year-old, male, Labrador retriever was referred for removal of a spindle cell sarcoma involving the right jugular vein. A CT scan showed a seven-centimeter subcutaneous mass consistent with a primary intravascular tumor of the jugular vein. The mass was resected, and histological evaluation was consistent with grade II intravenous spindle cell sarcoma of the jugular vein. Immunohistochemical positivity for vimentin, desmin, and αSMA antibody and negativity for S-100 protein suggested venous leiomyosarcoma. The dog received five doses of intravenous doxorubicin, and there was no recurrence of the tumor 30 months post treatment.
In dogs, primary intravascular sarcomas are rare and primary venous leiomyosarcoma has not been described. A venous tumor should be part of the differential diagnosis in dogs with ventral neck swelling.

Key words: dog, jugular vein, intravascular sarcoma, leiomyosarcoma, doxorubicin