Abstract
A primary cerebellar tumor found in a 14-week-old Sprague-Dawley rat, was noted to be extremely cellular and consist of small undifferentiated cells with hyperchromatic or vesicular nuclei and scanty cytoplasm. Mitotic figures were frequently observed. Solid masses of neoplastic cells were often separated by thin fibro-vascular septa, and a few pseudorossets were present. Many myoblasts were seen in a certain portion of the tumor. The tumor was diagnosed as medullomyoblastoma, a variant of medulloblastoma.
