PMC8645472_01
MRI Brain with contrast revealed a mass adjacent to the brainstem at the level of the medulla hypointense on axial T1-weighted sequences (a) with heterogeneous enhancement on the post-contrast sequence (b) and edema noted on T2 enhancing (c) and FLAIR (d) sequences.
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F1
MRI of the brain with contrast revealed a 2.5 cm heterogeneously enhancing, extra-axial, well-defined mass with cystic components in the left CPA causing mild to moderate mass effect on the left-sided pons, anterior cerebellar hemisphere, and middle ear cerebellar peduncle [Figure 1].
Hematoxylin and eosin-stained sections from surgical pathology revealed a non-infiltrating glial neoplasm with round to ovoid cells arranged in perivascular pseudorosette formations (a, x40). Tumor cells were diffusely positive for glial fibrillary acidic protein (b, x20) and epithelial membrane antigen in a scattered, dot-like perinuclear distribution (c, x20). A Ki-67 proliferation index highlighted up to 15% of tumor cell nuclei (d, x10). Based on these findings, a diagnosis of WHO Grade II ependymoma was made.
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F2
Immunohistochemistry revealed tumor cells diffusely positive for glial fibrillary acidic protein and S100 with scattered positivity for Olig2 and epithelial membrane antigen (dot-like perinuclear), and a Ki-67 proliferation index highlighted up to 15% of tumor cell nuclei [Figure 2].
The planning target volume (PTV) consisted of the resection cavity (outlined in orange) plus a 3 mm margin (outlined in red) as identified on the T1 post-contrast sequence (a). 100% of the dose was prescribed to this volume. A 3-arc volumetric modulated arc therapy technique with 6-MV photons was used to cover the volume with the 100% isodose line (5400 cGy) (in yellow) covering the PTV target (resection cavity + 3 mm margin) (in red) on the planning CT head (b).
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F3
A dose of 5400 cGy in 30 daily fractions was prescribed to the planning target volume which consisted of the resection cavity plus a 3 mm margin as identified on the T1 post-contrast MRI sequence [Figure 3].
Axial T1-weighted post contrast MRI sequence at the level of the brainstem 24 months after resection demonstrated no residual or recurrent gross disease.
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F4
Twenty-nine months after resection, the patient has had no clinical or radiographic evidence of treatment related toxicity or recurrent disease [Figure 4].