Hematomas in the thymus in dogs

Twenty dogs with a hematoma of the thymus are described. In four dogs the cause of the hematoma was a ruptured dissecting aneurysm of the aorta and in three cases the dogs had been hit by cars. In seven dogs the necks were overstretched by different factors. One dog was hit by a stone. In two dogs no anamnestic data were available, and in the last three cases, according to owner's statements, no trauma had occurred before the first signs. Thymic hemorrhages in the dog should not be considered to be a circumscribed pathogenetic entity. Indications are offered that trauma, or even commonly occurring microtrauma, can be involved in the pathogenesis of the hematomas in the thymus.