Cardiac Chemodectoma With Recurrent Pericardial Effusion and Cardiac Tamponade in an Alaskan Malamute: A Case Report.

Chemodectomas (aortic body tumors) are rare, slow-growing neoplasms arising from chemoreceptor tissue at the heart base in dogs, most frequently reported in brachycephalic breeds; to the authors' knowledge, their occurrence in nonbrachycephalic large breeds, such as the Alaskan Malamute, is uncommonly documented. An 8-year-old intact male Alaskan Malamute (body weight 44.8 kg) was referred with a history of lethargy, inappetence, exercise intolerance, and ascites. Echocardiography confirmed extensive pericardial effusion with cardiac tamponade and a multinodular, irregularly shaped heart-base mass invading the left atrium, right atrium, left auricle, and aortic root. The dog underwent two pericardiocentesis procedures, yielding 350 and 630 mL of serosanguinous fluid on Days 1 and 15, respectively. The dog died prior to the scheduled 1-week re-evaluation. Postmortem examination confirmed a multinodular, irregularly shaped, extensively invasive mass involving all cardiac chambers and the aortic root, with histopathological features morphologically consistent with chemodectoma. This case documents a fatal cardiac chemodectoma in an Alaskan Malamute, contributing to the limited literature on heart-base tumors in nonbrachycephalic large breeds, and emphasizes the importance of thorough echocardiographic evaluation, serial imaging in dogs with recurrent pericardial effusion, and counseling regarding a guarded-to-poor prognosis with extensive cardiac invasion.