Collagenous choristoma at the cerebellar peduncle of a Nelore bull

Resumo

Choristomas are mature normal tissues in abnormal anatomical positions. Reports in domestic animals are uncommon to rare, usually restricted to cattle, with the proliferation of different tissues in various locations, such as subcutaneous tissue, thoracic cavity, retroperitoneal and ocular regions. No age range is predominantly affected, but there are more reports in young cattle. The Laboratory of Veterinary Pathology at the Universidade Federal do Rio Grande do Sul received a brainstem sample of a bull, Nelore breed, 5 years old, from the project of Supplementary Diagnostic Methods of Transmissible Spongiform Encephalopathies (TSEs). The animal presented recumbency at the time of slaughter; was alert, with a complete fracture to the right femur and without neurological signs. On gross examination, there was a white oval firm mass, located caudally to the left caudal colliculus, on the left cerebellar peduncle. In the microscopic examination, there was a well-demarcated area, unencapsulated and composed predominantly of connective tissue fibers (collagen). Immunohistochemical examination for glial fibrillary acidic protein was negative. Due to the gross and microscopic characteristics, a diagnosis of collagenous choristoma at the cerebellar peduncle was established, since the presence of collagen within the brain tissue itself is abnormal.