case_images: PMC9062930_01
case_images: Magnetic resonance imaging (MRI) and intraoperative findings of a 59-year-old woman with a right cerebellopontine angle epidermoid cyst, before its malignant transformation (a-d) Preoperative MRI displayed a low-intensity signal on T1-weighted imaging, a high-intensity signal on T2-weighted imaging, and a high-intensity signal on diffusion-weighted imaging (DWI) without enhancement on contrast enhanced T1-weighted imaging. (e) The tumor contents (*) were pearly white debris, and the tumor capsule was a translucent thin membrane, most of which could be easily removed from the surrounding tissue. (f) A small portion of the capsule was left because of its tight adhesion to the facial nerve. (g) Postoperative MRI displayed no obvious residual tumor. MRI sequences in (a) is T1-weighted images. MRI sequences in (b) are T2-weighted images. MRI sequences in (c and g) are DWI. MRI sequences in (d) are contrast-enhanced T1-weighted images. C=Tumor capsule; V=Trigeminal nerve; VI=Abducens nerve; VII=Facial nerve; VIII=Vestibulocochlear nerve.
case_images: SNI-13-135-g001.jpg
case_images: PMC9062930_01_SNI-13-135-g001.jpg
case_images: F1
case_images: The lesion showed a low-intensity signal on T1-weighted imaging, a high-intensity signal on T2-weighted imaging, and a high-intensity signal on diffusion-weighted imaging (DWI) [Figures 1a-c]. T1-weighted imaging [Figure 1d]. The tumor contents were pearly white debris and could easily be aspirated [Figure 1e]. The tumor capsule was a translucent thin membrane that could easily be removed from the surrounding tissue, but a small portion of the capsule was left because it was tightly adhered to the brainstem and facial nerve (near-total removal) [Figures 1f and g].
case_images: Magnetic resonance imaging (MRI) and intraoperative findings of a 59-year-old woman with a right cerebellopontine angle epidermoid cyst, after its malignant transformation (a-c) MRI 6 years after the initial surgery displayed slight characteristics of recurrence. The lesion showed a low-intensity signal on T1-weighted imaging, a heterogeneous low-intensity signal on T2-weighted imaging, and a low-intensity signal on DWI. (d-i) MRI 8 years after the initial surgery displayed a contrast effect on the tumor capsule, suggesting malignant transformation. (j) The tumor contents (*) were yellowish and flaky debris, unlike that of the initial surgery. (k) The tumor capsule was a thick and cloudy membrane that tightly adhered to the surrounding cranial nerves and brainstem. MRI sequences in (a and d) are T1-weighted images. MRI sequences in (b and e-g) are T2-weighted images. MRI sequences in (c) and (h) are DWI. MRI sequences in (i) is contrast-enhanced T1-weighted images. C=Tumor capsule; VII=Facial nerve; VIII=Vestibulocochlear nerve.
case_images: SNI-13-135-g002.jpg
case_images: PMC9062930_01_SNI-13-135-g002.jpg
case_images: F2
case_images: On MRI at that time, the lesion showed a low-intensity signal on T1-weighted imaging, but unlike the MRI findings before recurrence, the lesion showed a heterogeneous low-intensity signal on T2-weighted imaging, and a low-intensity signal on DWI [Figures 2a-c]. MRI showed contrast effects of the tumor capsule on contrast-enhanced T1-weighted imaging [Figures 2d-i]. Moreover, edema around the brainstem owing to tumor compression was also observed. Unlike the tumor that had been removed initially, this tumor contained yellowish and flaky debris and could not be easily aspirated [Figure 2j]. The tumor capsule was also a thick and cloudy membrane that tightly adhered to the surrounding cranial nerves and brainstem and was subtotally removed [Figure 2k].
case_images: Histopathological findings of the tumors removed at the first (a-d) and second (e-h) surgeries (a) Hematoxylin and eosin staining showing a cyst with a lining composed of stratified squamous epithelium with a granular layer and abundant lamellated keratin flakes. The squamous epithelium shows multilayered squamous metaplasia in some regions, resulting from the proliferation of basal cells. These squamous cells show mild atypical features and loss of cell polarity (original magnification: x200). (b-d) Immunohistochemical analysis (b: Epithelial membrane antigen (EMA), x200; c: p53, x200; d: p16, x400). The stratified squamous epithelial cells show partial positive staining for EMA, and 70% to 80% of the cells were positive for p53 and 10% to 20% of the cells were positive for p16. (e and f) Hematoxylin and eosin staining showing the cyst lining composed of stratified squamous epithelium with a granular layer and abundant lamellated keratin flakes. (e) In many parts of the cyst lining, the squamous epithelium shows multilayered metaplasia of atypical squamous cells, with a few mitotic figures (e and f: original magnification x200) (g and h) Immunohistochemical analysis (g: p53, x200; h: p16, x200). Almost all atypical squamous cells were positive for p53, and 30-40% of the cells were positive for p16.
case_images: SNI-13-135-g003.jpg
case_images: PMC9062930_01_SNI-13-135-g003.jpg
case_images: F3
case_images: The cyst lining demonstrated multilayered squamous metaplasia owing to the proliferation of basal cells with mild nuclear atypia [Figure 3a]. IHC analysis revealed that these atypical squamous epithelial cells had partial loss of staining for epithelial membrane antigen (EMA), 70-80% of the cells were positive for p53, and a few cells were positive for p16 [Figures 3b-d]. At the time of the second surgery, histological analysis revealed that the cyst lining had typical epidermoid features, and in many parts the cyst lining showed multilayered squamous metaplasia with atypical features, such as the loss of cellular polarity and few mitotic figures [Figures 3e and f]. IHC analysis revealed that almost all of the atypical squamous epithelial cells were positive for p53, and 30-40% of the cells were positive for p16 [Figures 3g and h].