Case Report: Diagnostic challenge in an intradural tumor with a neuroendocrine pattern and diffuse neuraxial enhancement

Cauda equina neuroendocrine tumor (CENET) is a rare central nervous system (CNS) World Health Organization (WHO) grade 1 neoplasm that usually forms a circumscribed lumbar intradural mass. A young adult woman developed rapidly ascending weakness over 15 days, severe headache, and sudden bilateral visual loss. Examination documented grade IV papilledema; retinal detachment was also listed, but its relationship to the papilledema and acute visual loss was not established. Magnetic resonance imaging showed diffuse enhancement of the conus medullaris, filum terminale, and cauda equina to S2; a separate T11 lesion; and two posterior fossa extra-axial lesions. Only the lumbar lesion was sampled; a shared origin was not established. Cerebrospinal fluid cytology was negative for malignant cells. After medical stabilization, an L1–L3 laminectomy and excision of an intradural lesion were performed. At discharge, the patient was hemodynamically stable, and her condition was recorded as improved; objective neurologic and visual outcomes were not documented. Subsequent external neuropathology review found organoid, trabecular, papillary, and pseudorosette-like growth with neuroendocrine chromatin and spindle cells resembling sustentacular cells. Immunohistochemistry showed focal synaptophysin, patchy SSTR2 and GFAP, OLIG2 positivity, rare paranuclear dot-like pancytokeratin staining, and negative chromogranin A, INSM1, and EMA; the reported Ki-67 index was 18%. The external review favored CENET, CNS WHO grade 1, on morphologic and immunohistochemical grounds; molecular testing was not performed. However, the discordant glial immunophenotype and diffuse neuraxial pattern overlap with diffuse leptomeningeal glioneuronal tumor, and the retinal and multifocal findings also raise the untested possibility of hemangioblastoma in the setting of von Hippel–Lindau disease. This case supports cautious integration of expert pathology review with targeted ancillary testing and cautions against assigning grade based on Ki-67 alone.