PMC9282763_01
Contrast-enhanced magnetic resonance imaging (CE-MRI) findings of the cerebellopontine angle lesion. (a) Images taken on the first consultation showed a suspicious lesion of about 12 mm in size, resembling a vestibular schwannoma, at the right cerebellopontine angle. (b) CE-MRI images 2 years after the first consultation (13 months before admission) showed no change in the tumor size. (c) CE-MRI images taken 7 months before admission showed an intratumoral cyst and tumor growth to 20 mm. (d) CE-MRI taken 1 month before admission showed intratumoral hemorrhage, edematous changes in the right cerebellum, and tumor growth to 27 mm.
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F1
Since it was located along the VII and VIII nerves and the right internal auditory canal appeared dilated on imaging, it was diagnosed as vestibular schwannoma [Figure 1a]. During follow-up, the tumor gradually increased in size, with some intratumoral hemorrhagic changes [Figures 1b-d].
Imaging findings on the day of admission. Computed tomography scan (a), contrast-enhanced magnetic resonance imaging (CE-MRI) (b), and fluid-attenuated inversion recovery (c) images on the day of admission showing the tumor (arrow), hemorrhage (arrowhead), and extensive edematous changes in the right cerebellum. CE-MRI (d) showed the enlargement of lateral ventricles.
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F2
Computed tomography (CT) scan and MRI revealed tumor growth, edematous changes in the right cerebellum, and hydrocephalus [Figure 2].
Histological findings indicating metastatic neuroendocrine tumors. Hematoxylin and eosin staining showed monotonous tumor cells with round nuclei and eosinophilic cytoplasm arranged in nested or trabecular pattern (a). Immunohistochemically, tumor cells were positive for cytokeratin (b), synaptophysin (c), and CD56 (d), although they were negative for chromogranin A (e). Ki-67 labeling index was 5.7% (f).
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F3
Histopathological examination revealed metastatic NET comprising monotonous tumor cells arranged in nested or trabecular pattern [Figure 3a], with features similar to those of previous metastatic lesions in the brain. Immunohistochemically, these cells were positive for cytokeratin [Figure 3b], synaptophysin [Figure 3c], and CD56 [Figure 3d], and negative for chromogranin A [Figure 3e]. Ki-67 labeling index was 5.7% [Figure 3f].
Postoperative imaging findings. Contrast-enhanced magnetic resonance imaging on the next day after the surgery (a and b) showing partial resection of the tumor. T1-weighted MRI 11 months after surgery (c and d) showing a reduction in the size of the residual lesions.
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F4
Residual lesions [Figures 4a and b] were stereotactically irradiated with 35 Gy in five fractions on days 33-37.