Hamartoma in the medulla oblongata with marked mineral deposits in a dog.

A mass lesion in the medulla oblongata in a 9-year-old female Golden Retriever was examined pathologically. The medullary mass was 1 to 2 cm in diameter and poorly demarcated. The cut surface was discolored with numerous sand-like materials. Histologically, the mass lesion consisted of complex proliferation of irregularly arranged vessels as well as astrocytes with numerous mineral deposits. The astrocytic components exhibited no apparent anaplastic morphology. The proliferating vessels were either veins with muscle layer and capillaries. A few axons and myelinated fibers were also found in the lesion. The number of ki-67-positive cell nuclei was extremely small, suggesting the poor growth activity of these cells. Based on the findings, the lesion was considered to be a non-neoplastic, hamartomatous change.