Metastatic tonsillar squamous cell carcinoma in the distal humerus of a dog

ABSTRACT A 14‐year‐old neutered male, bearded collie was presented with acute respiratory difficulty. Further investigation identified a large, ulcerated tonsillar mass, and biopsy confirmed the diagnosis of tonsillar squamous cell carcinoma (TSCC). Computed tomography (CT) supported this finding and revealed left‐sided retropharyngeal lymphadenopathy. Surgical removal of the affected tonsil and lymph node was performed, and the dog recovered well under medical management. At a follow‐up visit, a lesion was again noted in the left tonsillar area; histopathology confirmed recurrence of TSCC, which was managed medically. Seventeen months post‐initial presentation, the dog returned with left forelimb lameness. CT and arthrocentesis were suggestive of metastatic SCC in the distal humerus with extension into the elbow joint. Palliative amputation was performed with subsequent histology confirming TSCC metastasis. This case highlights a prolonged survival time of 556 days despite metastatic disease, in addition to a previously unreported metastatic site of TSCC.