Thymoma is a type of tumor that arises from cells of the thymus, an organ present in all mammals responsible for normal immune cell (T-lymphomcyte) maturation. These tumors are most common in older animals, and clinical signs associated with this type of tumor are often non-specific (i.e. lethargy, weight loss, etc) and rarely associated with a cough or respiratory difficulty until they grow large in size. Additionally, thymomas can also cause secondary or “paraneoplastic” metabolic and immune system dysfunction.
A preliminary diagnosis of thymoma is often made based on the location of the tumor and aspiration cytology. The importance of aspiration cytology cannot be understated because several different tumor types including lymphoma, a non-surgical disease, can appear very similar on imaging studies and can have identical clinical signs.
Other types of tumors that occur less frequently in this region include thyroid carcinoma, heart base tumors and others which are also important to diagnose prior to treatment, as the prognosis associated with these other tumor types are often not as favorable. Compared to many of the other potential tumor types that can occur in this region, thymoma carries a relatively good prognosis with treatment.
The treatment of choice for both canine and feline thymoma is surgery. In patients with relatively small masses, excision of the mass can be performed thorascopically as a minimally invasive manor; a procedure that is offered at Aspen Meadow Veterinary Specialists. For larger or more invasive masses, thoracotomy (opening of the chest either through the sterum (median sternotomy approach) or in between the ribs (intercostal approach) is often required.
For more information regareding canine or feline thymoma, please download a copy of our information sheet by clicking on the PDF logo.