MALIGNANT CAUDA-EQUINA PARAGANGLIOMA IN A CAT

An 11-year-old spayed female domestic long-haired cat presented for su rgical removal of a slowly growing and deeply invasive 2.5 x 3.5-cm ma ss cranial to the base of the tail. Light microscopic examination of s urgical biopsy specimens revealed an encapsulated mass composed of pac kets of polygonal cells of various sizes separated by a delicate fibro vascular stroma. Gomori's reticulum stain revealed a characteristic en docrine or ''Zellballen'' pattern. Tumor cells contained diffuse posit ive reactivity to synaptophysin and neuron-specific enolase, reactions consistent with a neuroendocrine neoplasm. S-100 protein-positive cel ls reminiscent of sustentacular (support) cells occurred singly or in small clusters within tumor packets. At postmortem examination 3 month s later, a 9- x 5- x 4-cm multinodular raised tan mass involving the c audal pelvis, sacrum, and tail-head regions was found. The base of thi s neoplastic mass originated within the cauda equina region and involv ed approximately five caudal nerve roots. Numerous 1-3-mm metastatic n odules were identified disseminated throughout the pulmonary parenchym a. The tumor was diagnosed as a malignant paraganglioma of the cauda e quina region with pulmonary metastasis.