Canine oral papillary squamous cell carcinoma with lymph node metastasis in a dog.

Canine oral papillary squamous cell carcinoma is a rare subtype of squamous cell carcinoma with low metastatic potential. This report describes a 6-month-old intact male Labrador retriever dog with a 2.2 × 2.1-centimeter intraoral mass located in the gingiva between the 1st and 2nd right mandibular premolars. Computed tomography revealed an exophytic mass infiltrating the mandible and right mandibular gingiva without evidence of regional lymph node enlargement or distant metastasis. Histopathological evaluation confirmed canine oral papillary squamous cell carcinoma with metastasis to the right mandibular lymph node (surgically removed) and carboplatin was administered postoperatively. At 1404 d post-surgery, no local recurrence or distant metastasis were observed. To the best of the authors' knowledge, this is the first reported case of canine oral papillary squamous cell carcinoma metastasizing to the lymph nodes. The dog was treated with chemotherapy after surgery and had a good long-term prognosis. Key clinical message: Canine oral papillary squamous cell carcinoma has not been reported to metastasize and is usually treated locally with surgery or radiation therapy. However, as in the case reported herein, metastasis to the lymph nodes may occur. In such cases, accurate evaluation of metastasis, including lymph node excision biopsy, and chemotherapy may need to be considered.