case_images: PMC11250673_01
case_images: a In T1-enhanced MR image, 4 x 3 cm sized round, rim-enhanced mass on left cerebellopontine angle. In temporal bone computed tomography, there is calcification around the mass (b) and passage (arrow) between semicircular-facial canal and posterior cranial fossa (c).
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case_images: F1
case_images: Brain computed tomography scan revealed a 4 x 3 cm calcified lesion on the left cerebellopontine angle, with mastoid bone erosion around the facial and semicircular canals; also, brain magnetic resonance imaging (MRI) showed a rim-enhanced mass with surrounding edema and central necrosis (Fig 1).
case_images: In diffusion weighted image (DWI), there is no marked restricted diffusion on lesion (a) and no low apparent diffusion coefficient (ADC) value (b).
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case_images: F2
case_images: Although it did not exactly match the condition with brain abscess in diffusion weighted image, as she had a history of otitis media 10 years ago and the computed tomography scan showed a passage connecting the middle ear to the posterior cranial fossa, we hypothesized that this lesion was a chronic brain abscess (Fig.2).
case_images: a, c Low power view demonstrates spindle cells proliferation in haphazard arrangement and chronic inflammatory cells. There are hyalinized stroma and calcification. b, d High power view demonstrates spindled myofibroblastic cells without overt atypia admixed with lympho-plasma cells.
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case_images: F3
case_images: A few mitoses were observed (<5 mitoses/10 HPF) (Fig. 3).
case_images: IHC shows reactivity for CD68 and SMA. Ki67 proliferation index is 17%.
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case_images: F4
case_images: The tumor had a 17% Ki67 proliferation index (Fig. 4).
case_images: Immediate postoperative MR image. Pre-enhanced T1 (a) and post-enhanced T1 (b). Subtotal resection was done.
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case_images: F5
case_images: One month after the surgery, MRI was done (Fig.5).