Primary pulmonary carcinoma in a dog presenting with hypertrophic osteopathy

A 9‐year‐old dog was presented for a 2‐month history of bilateral carpal, stifle and tarsal swelling and a large thyroid mass. Carpal radiographs indicated hypertrophic osteopathy, thoracic radiographs revealed an intrathoracic mass, fine‐needle aspirate of the thoracic mass diagnosed carcinoma, and subsequent cervical, thoracic and abdominal computed tomographies revealed widespread hypertrophic osteopathy, bilateral thyroid cystic structures and a soft tissue mass in the right cranial mediastinum or lung. After unilateral thyroidectomy and thoracotomy for a lung lobectomy and mediastinal lymph node extirpation, the dog was diagnosed with a benign cyst of the thyroid and a completely excised grade II pulmonary carcinoma with no metastasis to the mediastinal lymph node. After 135 days of presentation, the dog presented with increased respiratory effort, and pleural effusion was diagnosed. Thoracocentesis was performed, and cytology of the fluid was concerning for carcinoma. The dog further declined rapidly and was euthanased 178 days after the initial presentation.