Clinical history: A 20-year-old male with no past medical history presented with lower back pain and tingling sensation in both lower limbs. MRI showed an intradural mass within the lumbar spine; imaging findings were suggestive of a schwannoma. The patient underwent excision of the mass with intraoperative frozen section. Intra-operative crush prep smears were made.
Cytologic findings
- 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
Differential diagnoses
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
- Meningioma
- 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
- Ependymoma
- Others
- Metastatic tumour
- Morphology depends on the primary tumour
- Less likely given the young age and absence of previous history of malignancy
- Metastatic tumour
Reference: Lacruz C. R., et al. Central Nervous System Intraoperative Cytopathology. 2nd Edition. Springer International Publishing, 2018.
Histologic findings
The subsequent paraffin sections of the tumour are as follows:
- 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.
Diagnosis
Diagnosis: Ependymoma
Case writer: Dr Hui Min Tan
