Cytokeratins expression in paragangliomas of the cauda equina

Background: Paragangliomas rarely involve the cauda equina region. In this location, these tumors can show misleading morphological features such as t rabecular or papillary growth patterns and variable expression of cytokerat ins. Methods: We comparatively studied the immunohistochemical and ultrastr uctural patterns of 3 paragangliomas of the cauda equina (PCE) and of 8 par agangliomas from other sites. Results: All the paragangliomas expressed neu roendocrine markers (neuron-specific enolase, chromogranin A, synaptophysin and neurofilament protein). In PCE, chief cells exhibited a strong positiv ity with a broad spectrum anti-cytokeratin antibody. The staining was diffu se in the cytoplasm or had a paranuclear dot-like disposition. In other sit es, only one paraganglioma showed a focal expression of cytokeratins. At ul trastructural level, chief cells of PCE contained characteristic dense core granules and intermediate-sized filaments sometimes grouped in paranuclear whorls. Conclusion: The dual immunophenotype of PCE, paraganglionic and ep ithelial, must be recognized in order to distinguish these tumors from, for example, a metastasis of a neuroendocrine carcinoma. PCE an slow-growing t umors and have mostly a favorable prognosis after complete surgical excisio n.