Surgical Treatment of Thymic Disease

Thymic disease is uncommon, but when encountered, surgery is most often the treatment of choice. The thymus is located in the cranial mediastinum in a cranioventral location. Thymic pathology is most often noted incidentally in dogs and cats during routine geriatric thoracic radiographic screening. Because of the location of the thymus in the cranial mediastinum and its relative proximity to the respiratory tract, clinical signs seen with thymic disease include dyspnea, coughing, and dysphonia. The most commonly described paraneoplastic syndrome that occurs in conjunction with thymoma is myasthenia gravis. Myasthenia gravis occurs when acetylcholine receptors are targeted by autoantibodies. Myasthenia gravis can also result in megaesophagus, which can cause regurgitation; this likely occurs due to dysfunction of the striated muscle of the canine esophagus. A cystic thymus has been reported in two other feline cases: one in conjunction with myasthenia gravis and one associated with thymic hyperplasia.