Presentation
Increasing sciatica and urinary retention.
Patient Data
MRI demonstrates an intradural extramedullary tumor located at the L4 level and extending two vertebral body lengths. It completely fills the canal and remodels the posterior aspect of L4 (vertebral scalloping). It is of intermediate signal on both T1 and T2 weighted images and demonstrates homogenous vivid enhancement. Inferior to the mass, trapped CSF has high T1 and T2 signal, possibly due to high protein content.
An enhancing mass ( * ) is associated with extensive bony remodeling (blue arrows) including posterior vertebral body scalloping. Prominent flow voids are seen anterior to the conus (red arrows).
Inferior to the mass, fluid (yellow arrows) which is high on T2 is also high on T1 suggesting either blood product or proteinaceous material (absence of signal drop out on T2 images suggests the latter).
The patient went on to have a laminectomy and excision of the tumor.
Histology
MICROSCOPIC DESCRIPTION : The sections show a well circumscribed tumor, with peripheral fibrosis and some evidence of previous hemorrhage. This consists of sheets of cells with a prominent pattern of perivascular pseudorosetting and, due to the prominent arborising vascularity, areas with a nested appearance. Individual tumor cells are polygonal or columnar, the latter morphology particularly associated with blood vessels, with cytoplasm directed towards the vessel and basally located nuclei. The cytoplasm is pale amphophilic. Nuclei are generally rounded with granular or finely vesicular nucleoplasm. Nucleoli, when present, are generally fairly small. Mitoses are seen, at a rate of approximately one per 10 hpf. In places a pseudopapillary appearance is imparted to the tumor by preservation of cells around blood vessels and separation in the intervening areas. In areas, the separation is facilitated by foci of tumor necrosis, interpreted as related to the surgical procedure.
Immunohistochemical stains have been done. The tumor cells are negative for GFAP, S100, CK20, CK7. There is focal staining for chromogranin, with strong staining for synaptophysin. Staining for high molecular weight cytokeratin (CAM 5.2) shows staining of occasional tumor cells. Small numbers of weakly S100 positive cells are present at margins of tumor groups.
The morphologic and immunohistochemical features strongly suggest a neuroendocrine neoplasm. At this location paraganglioma is a significant diagnostic consideration and immunostaining for chromogranin and synaptophysin as well as some staining for cytokeratin would be in accord with this diagnosis. An alternative diagnosis would be metastatic tumor from a neuroendocrine tumor elsewhere in the body, but in view of the radiologic evidence of chronicity of this lesion, that would appear an unlikely proposition (Note: no systemic disease present).
Case Discussion
Large slow growing spinal paraganglioma. In this case, the only clue to the diagnosis are the large flow voids over the conus.
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 spinal (or cauda equina) neuroendocrine tumor is preferred in the 5th edition (2021) WHO classification of CNS tumors.
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