Lung lobe torsion in association with a pulmonary papillary carcinoma in a dog

Lung lobe torsion (LLT) is an uncommon condition in dogs reported to be most commonly idiopathic or secondary to trauma, pleural effusion, lung lobectomy or thoracic neoplasia. Carcinomas are the most common primary lung tumours in dogs, but only a few cases have been reported in association with LLT in veterinary medicine. This case describes an adult male neutered Labrador, which presented with lethargy, weight loss and pleural effusion. Computed tomography (CT), cytology of the lung, thoracocentesis and fluid analysis were performed. CT revealed pleural effusion and torsion of the left cranial lung lobe with no evidence of a pulmonary mass or metastatic disease. Thoracotomy and left cranial lung lobectomy were performed. Intraoperatively there was no macroscopic evidence of pulmonary neoplasia. Histopathology of the lobar tissue confirmed grade 2 pulmonary papillary carcinoma. It is possible that early detection and surgical management might help to prevent the morbidity and mortality associated with LLT. However, as in this case, the underlying cause for the LLT will ultimately determine the patient's prognosis. The final diagnosis of papillary carcinoma in this case, was only made via histopathological assessment of the pulmonary tissue as it was unclear on the advanced imaging and macroscopic intraoperative evaluation of the lungs. This case highlights the importance of considering pulmonary neoplasia as a differential for LLT even in the absence of a macroscopic mass, and therefore the value of performing histopathology on the excised lung tissue.