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There is a heterogeneously enhancing mass that occupies the inferior fourth ventricle and extends through the foramen Magendie to lie posterior to the cervicomedullary junction. The medulla and cervico-medullary junction are mildly anteriorly displaced with partial effacement of the premedullary cistern. There is no upstream obstructive hydrocephalus. The mass is mildly hyperintense to cortex on T2, with multiple small T2 hyperintense foci that suppress on FLAIR, as well as containing multiple rounded foci of signal loss on 2D MERGE sequence which may represent calcifications or blood product or both. The ADC values within the enhancing component of the mass are approximately 1560mm2/s, although given the amount of T2* signal loss, these values should be interpreted with caution. No increased CBV (not shown; same caution due to T2* effects should be exercised) identified and MR spectroscopy is non-contributory (not shown).
Conclusion: The appearance is most consistent with an ependymoma although in this age group a subependymoma is more likely, although they are usually smaller and non-enhancing. Other entities (e.g. metastases, choroid plexus papilloma and hemangioblastoma) are all thought to be far less likely.
The patient went on to have surgery.
MICROSCOPIC DESCRIPTION: Sections show a variably cellular glioma composed of monotonous tumor cells set within a dense fibrillary stroma. Tumor cells demonstrate round nuclei with granular chromatin and inconspicuous nucleoli. There are scattered foci of dystrophic calcification present. No perivascular pseudorosettes, nuclear atypia or mitoses are seen. No necrosis or microvascular proliferation are seen. There is no evidence of malignancy.
FINAL DIAGNOSIS: Subependymoma (WHO grade I).
When it comes to ependymomas/subependymomas, age is a good guide as the two can look very similar.