Embryonal central nervous system tumor in the brain of a goose.

Embryonal central nervous system (CNS) tumor is a rare malignant neoplasm that arises from the neural crest. Herein we describe an embryonal tumor in the brain of an adult male domestic goose ( Anser anser) that was euthanized after a short history of wandering and lethargy. Grossly, a focal, bright-red, soft plaque was present on the ventral aspect of the brain, extending from the optic chiasm to the midbrain, as well as into the dorsal neuroparenchyma. Histologically, the nodule consisted of a poorly demarcated population of neoplastic cells arranged in streams and bundles, and occasionally palisading around small capillaries (pseudorosettes). Neoplastic cells were elongate and had scant, finely granular, eosinophilic cytoplasm, and elongate nuclei with dense chromatin. Mitoses were uncommon. Scattered foci of intratumoral necrosis and microvascular proliferation were present. Neoplastic cells were immunoreactive for doublecortin and neuronal nuclei. Ultrastructurally, neoplastic cells had elongated-to-polyhedral cytoplasm with short processes, scarce intermediate filaments, and small round mitochondria and rough endoplasmic reticulum. The cell membrane had varied numbers of intercellular anchoring-like junctions, and nuclei were round-to-elongate and had marginal aggregates of heterochromatin. Morphologic, immunohistochemical, and ultrastructural findings in our case are consistent with a poorly differentiated embryonal tumor.