Brain tumors with cysts causing head tilt and falling in dogs

Abstract

Tumoral macrocysts (grossly observable cysts) are common in human pilocytic astrocytomas but are rarely reported in canine astrocytomas. Here we describe 7 canine astrocytomas with macrocysts. The median age of affected patients was 9.6 y, and 2 dogs were brachycephalic. Clinical signs reported in 6 cases included head tilt (4 cases), falling (4 cases), and ataxia (3 cases). Gross changes consisted of well (5 cases) or poorly demarcated (2 cases), tan-to-pale-yellow masses with distinct, 2-10-mm fluid-filled cysts that expanded the cerebellum (4 cases) or telencephalon (3 cases). Histology and immunohistochemistry revealed low-grade astrocytoma in 6 cases and high-grade astrocytoma in 1 case. Neoplastic cells were elongate, formed bundles embedded in an eosinophilic fibrillary stroma, and had oval-to-elongate nuclei. Gemistocytic differentiation was common (4 cases). Cystic areas were lined by neoplastic astrocytes and were either apparently empty or contained scant, eosinophilic, proteinaceous material and a few neoplastic astrocytes, foamy macrophages, and occasionally other leukocytes. The mitotic activity was absent or low across cases. Cytoplasmic immunolabeling for glial fibrillary acidic protein was detected in 6 cases. Our findings indicate that canine cystic astrocytomas are rare (our cases span several decades) and are located mainly, but not exclusively, in the cerebellum.