A spine-tingling mass

• Cellular smears showing monotonous cells occurring in papillary-like tissue fragments, as discohesive aggregates and as singly dispersed cells, on a fibrillary background
• Some blood vessels seen within the cores of papillary fragments
• Rosette-like structures seen
• Tumour cells display round to ovoid nuclei, inconspicuous nucleoli and finely speckled chromatin, with fibrillary cytoplasmic processes

 
Here are some differential diagnoses based on the imaging findings:

• Intradural extramedullary spinal lesions
  • Meningioma
    • Uneven smears with large irregular clusters, small groups and single cells
    • Cells display ovoid nuclei, fine chromatin, small nucleoli, nuclear pseudoinclusions, and abundant cytoplasm with broad borderless cytoplasmic processes
    • Cells may be arranged in whorls
    • +/- Psammoma bodies
  • Schwannoma
    • Clusters of spindle cells with slender, wavy nuclei associated with fibrillary stroma
    • Nuclear palisading may be seen
    • Generally lack single cells in the background
• Intradural intramedullary spinal lesions
  • Ependymoma
    • Fibrillary tissue fragments and discohesive sheets of small and uniform cells with round to ovoid nuclei and finely speckled chromatin
    • Ependymal rosettes and perivascular pseudorosettes
• Others
  • Metastatic tumour
    • Morphology depends on the primary tumour
    • Less likely given the young age and absence of previous history of malignancy

Reference: Lacruz C. R., et al. Central Nervous System Intraoperative Cytopathology. 2nd Edition. Springer International Publishing, 2018.

• Cellular tumour composed of sheets of monomorphic-appearing cells with uniform round nuclei
• Perivascular pseudorosettes are seen
• No hypercellularity, increased mitotic activity, necrosis or microvascular proliferation is identified
• The neoplastic cells show cytoplasmic dot-like expression of EMA and D2-40. They are also positive for GFAP and S100 (patchy). SOX10 immunostain is negative.

 
Ependymoma