The patient went on to have a resection.

Histology

The sections show a well-circumscribed tumor composed of nests and cords of tumor cells amongst a prominent vascular network. The tumor cells are monomorphic with round-oval nuclei and fine-speckled chromatin, and most have an epithelioid appearance. There are vague perivascular pseudo-rosettes. There is no myxoid material or papillary architecture.

By immunohistochemistry, the tumor cells are positive for synaptophysin and chromogranin A, and negative for EMA and GFAP. 5100 and SOX10 highlight scattered single cells. The tumor cells show intact staining for SDHA and SDHB indicating that SDHX mutation is unlikely.

The lesion appears to have been shelled out with very narrow (<0.1mm) but clear margins in the planes examined.

Final diagnosis

paraganglioma of the filum terminale (WHO grade 1) - now known as a cauda equina neuroendocrine tumor.