PMC8721377_01
(a) Axial CT of the head with no lateral semicircular canal present. (b) Axial CT of the head showing a hypoplastic cochlea. (c) Axial T1-weighted MRI of the head without gadolinium revealing a mastoid lesion with bright signal. (d) Axial T2-weighted MRI of the head with bright signals from both components of a mastoid lesion.
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There was no lateral semicircular canal (Figure 1(a)) and the cochlea appeared hypoplastic (Figure 1(b)). The cystic structure was non-enhancing on T1 with gadolinium and bright on T1 without gadolinium (Figure 1(c)) and T2 (Figure 1(d)), suggesting internal fluid with protein content.
(a) Pre-excision view of the mastoid cystic mass. (b) Post-excision view of the remaining bony shell and underlying facial nerve after complete resection of the mastoid cystic mass.
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On gross inspection, the tumor was red-brown in color with multicystic compartments filled with gelatinous fluid (Figure 2a). Distinct thick bony shell, possibly due to long-term bony remodeling, was noted peripherally (Figure 2b).
Low-powered (x40) view of simple columnar epithelium with goblet cells and two submucosal muscular layers (trichrome stain).
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A trichrome stain highlighted fibrosis and muscular tissue, and desmin immunoreactive smooth muscles were seen in two distinct submucosal layers, resembling the muscularis mucosa and muscularis propria (Figure 3).