Killian, a six year old male castrated Great Dane, presented to the Oncology Service for evaluation of a firm mass in the right ventral cervical region. The mass was noticed incidentally by the owner approximately four weeks prior to presentation, and was not causing any clinical signs. On presentation, Killian was bright, alert, and responsive. Physical examination revealed a grossly visible right-sided mass in the region of the thyroid gland. Upon palpation, the mass was firm, freely movable, non-painful, and measured approximately 5.4 x 7.5 x 2.5 cm. Peripheral lymph nodes were within normal limits, and thoracic and cardiac ausculations were unremarkable. Killian was in good body condition, and except for the cervical mass, he seemed to be in good health. Differential diagnosis for a ventral cervical swelling includes thyroid tumor, lymphatic metastasis of tonsilar squamous cell carcinoma, lymphoma, hemangiosarcoma, carotic body tumor, abscess or granuloma, and salivary mucocele. Complete blood count and chemistry panel were with normal limits. Three-view thoracic radiographs revealed no abnormalities. Fine needle aspirate of the mass was bloody grossly. Microscopic examination of the fine needle aspirate revealed mostly red blood cells with platelet and fibrin clumps. However, neoplastic epithelial cells with large nuclei and moderate amount of cytoplasm were also found. These cells exhibited moderal anisokaryosis. Cytologic diagnosis of epithelial neoplasia, combined with Killian's age, species, and the location and the firm consistency of the mass, made thyroid carcinoma highly likely.