Complete response to toceranib phosphate treatment in a dog with an intranasal mast cell tumour

Intranasal mast cell tumours (MCTs) are rare in dogs and are diagnostically and therapeutically challenging. This case describes a 13‐year‐old spayed female Chinese Native Dog presenting with facial swelling and bilateral submandibular lymphadenopathy. Fine‐needle aspiration identified a round cell neoplasm with eosinophilic infiltration, and histopathology with toluidine blue staining confirmed intranasal MCT. The tumour was classified as T 1 N 1 M 0 and was most consistent with WHO stage IIa. Toceranib phosphate was administered orally at approximately 2.63 mg/kg per dose three times weekly, resulting in complete resolution of the facial mass within 7 days, accompanied by regression of lymphadenopathy and no recurrence during follow‐up. Mild, self‐limiting vomiting developed at week 4 and was managed with cimetidine. The dog died suddenly 89 days after treatment initiation from an undetermined cause without postmortem examination. This case highlights the potential of toceranib as a treatment option for intranasal MCTs in anatomically challenging locations and supports further clinical evaluation.