Cauda equina neuroendocrine tumor

Case contributed by Frank Gaillard
Diagnosis certain


Bilateral leg pain. Patient allergic to gadolinium.

Patient Data

Age: 45 years
Gender: Male

A large intradural mass occupies much of the lumbar canal, below the tip of the conus, with evidence of bony remodeling. It is slightly hyperintense on T2 weighted imaging and isointense to cord on T1 with very large flow voids. Contrast was not administered as the patient had had an allergic reaction. 

The mass is associated with very large serpiginous flow voids, both related to the mass as well as on the surface of the conus. 

Annotated image

A large mass ( * ) fills and slightly expands the canal (orange dotted line) and is associated with very prominent vascular flow voids (red arrows). 

The patient went on to have a laminectomy and excision of the mass. 


Macroscopic Description: Specimen A is received in a single container and description "intradural tumor of cauda equina" and consists of resection of a smooth red-brown lesion measuring 4 x 2 x 1.5 cm.

Microscopic Description: Sections show a circumscribed, highly vascular neoplasm composed of in some areas of tumor cells arranged in between fibrovascular septate. In most areas, the cells are arranged around thickened, hyalinized blood vessels. Both medium and large diameter blood vessels are seen within the lesion. The tumor cells have round to ovoid vesicular nuclei with a "salt and pepper"- like chromatin pattern with inconspicuous nucleoli. The cells have moderate amounts of granular eosinophilic cytoplasm. There is evidence of both acute and chronic hemorrhage. Mitotic figures are rare. Reticulin stain highlights the extensive vascularity of the lesion but there are nests of tumor cells devoid of reticulin production. The tumor is immunonegative for GFAP and strongly and diffusely immunopositive for synaptophysin. There is focal cytoplasmic expression of chromogranin. Only scattered cells are immunopositive for S100. In addition, S100 immuno-positivity is also seen in fine processes within the tumor. MIB1 labeling shows only scattered positive cells.

FINAL DIAGNOSIS: paraganglioma of the cauda equina. 

Case Discussion

This case illustrates fairly typical appearances of a large cauda equina neuroendocrine tumor

Note: These tumors were previously known as spinal paragangliomas however they are molecularly and genetically distinct from paragangliomas seen elsewhere in the body and as such the term neuroendocrine tumor is preferred in the 5th edition (2021) WHO classification of CNS tumors

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