Cauda Equina Neuroendocrine Tumor: A Histopathological Case Report.

Cauda equina neuroendocrine tumors (CENET) are rare neoplastic processes that develop in the cauda equina or filum terminale region of the spinal cord, which in previous incarnations of the World Health Organization (WHO) classification of the central nervous system (CNS) tumors were designated as paragangliomas. The change of terminology was carried out due to the rarity of the condition, its specific place of origin, the non-specific clinical and imaging characteristics with which the tumors present, and differences in biological properties (secretion and progression) as well as some minor differences in immunohistochemical protein expression patterns. Herein, we present a case of a male patient in his sixties who presented to us for a histopathological consultation of a previously excised tumor, which was grossly well-demarcated and connected to a nerve root in the cauda equina region. The tumor presented with histomorphological features of a sharply demarcated, non-infiltrative tumor growing in a nested to pseudopapillary pattern with a highly vascularized, intersecting stroma. Tumor cells were mildly atypical ovoid ones, with eosinophilic cytoplasm, central hyperchromatic nuclei, some with nucleoli, and salt and pepper chromatin. Intersecting stroma was rich in reticulin fibers, and the cell did not express epithelial membrane antigen, excluding the diagnosis of ependymoma as well as glial markers, excluding glial origin. Pan-cytokeratin was focally positive, neuroendocrine markers were diffusely positive, and the proliferative index was low. As such, the diagnosis of CENET, WHO CNS grade 1 was established, and the patient was referred back to the institution at which the surgery was performed for follow-up and further management.