Cytokeratins expression in paragangliomas of the cauda equina

Paragangliomas rarely involve the cauda equina region. In this location, these tumors can show misleading morphological features such as trabecular or papillary growth patterns and variable expression of cytokeratins.

We comparatively studied the immunohistochemical and ultrastructural patterns of 3 paragangliomas of the cauda equina (PCE) and of 8 paragangliomas from other sites.

All the paragangliomas expressed neuroendocrine markers (neuron-specific enolase, chromogranin A, synaptophysin and neurofilament protein). In PCE, chief cells exhibited a strong positivity with a broad spectrum anti-cytokeratin antibody. The staining was diffuse in the cytoplasm or had a paranuclear dot-like disposition. In other sites, only one paraganglioma showed a focal expression of cytokeratins. At ultrastructural level, chief cells of PCE contained characteristic dense core granules and intermediate-sized filaments sometimes grouped in paranuclear whorls.

The dual immunophenotype of PCE, paraganglionic and epithelial, must be recognized in order to distinguish these tumors from, for example, a metastasis of a neuroendocrine carcinoma. PCE are slow-growing tumors and have mostly a favorable prognosis after complete surgical excision.