Intra-cerebellar schwannoma with various degenerative changes: a case report and a systematic review

Abstract

Background: Intra-cranial schwannomas account for less than 8% of brain tumors, among which more than 80% arise from the vestibular nerve. Intra-cerebellar schwannomas are extremely rare. Several cases have been previously reported but without remarkable degenerative changes on histology.

Case presentation: A 61-year-old man presented with worsening disorientation, and an imaging study revealed a cystic lesion (6.5 cm in the largest diameter) in the left hemisphere of the cerebellum accompanied by a mural nodule (2.5 cm) located just inside the skull with enhancement and focal calcification, in addition to hydrocephalus. The lesion was more than 5 mm from the left acoustic nerve. The patient underwent gross total resection. Pathological examination revealed remarkable degenerative changes with various morphological features. Tumor cells were pleomorphic with rich cytoplasm containing numerous eosinophilic granules. Blood vessels and extracellular matrix showed remarkable hyalinization. Immunohistochemical staining revealed that the tumor cells were positive for S-100 protein and negative for Olig2. The tumor was diagnosed as a schwannoma with marked degenerative changes.

Conclusions: The present case is discussed with reference to a systematic review of previous reports of intra-cerebellar schwannoma. Intra-cerebellar schwannoma should be included in the differential diagnosis of cystic lesions with heterogeneous histopathological morphology in the cerebellum.

Keywords: Ancient schwannoma; Eosinophilic granular inclusions; Intra-cerebellar schwannoma; Schwannoma with degenerative changes.

Fig. 1

Pre-operative images of computed tomography (CT) scans and magnetic resonance imaging (MRI). a CT revealed a cystic lesion with a mural nodule in the left hemisphere of the cerebellum. The lower panel shows a magnified image of the area within the red rectangle in the upper panel. The nodular component was accompanied by a high attenuated area, suggesting focal calcification. Hydrocephalus was associated with a shift of the fourth ventricle to the right. b Contrast-enhanced CT showed mild enhancement in the mural nodule. The lower panel shows a magnified image of the area within the red rectangle in the upper panel. c, d MRI demonstrated that the cystic lesion was hypointense on a T1-weighted image (c) and hyperintense on a T2-weighted image (d). The tumor was well-defined, and no peritumoral brain edema was present. e T2 star-weighted image shows a hemorrhage within the cyst and in the mural nodule. f Fluid-attenuated inversion recovery image shows hydrocephalus with periventricular hyperintensity

Fig. 2

Macroscopic views of the cerebellar tumor. a The surface of the tumor was moderately swollen with a cystic component filled with brownish fluid, implying a history of intra-cystic bleeding. b The boundary of most of the tumor was clear. The tumor was resected totally after detachment from the cerebellum

Fig. 3

Histopathological examination of the excised tumor. a Low-power view of the excised tissue with hematoxylin and eosin staining. On the periphery of the tumor tissue, cystic components were observed. b Middle-power view of the tumor tissue. Tumor cells were intermingled with hyalinized blood vessels. c-e High-power view of the tumor cells. The tumor cells were pleomorphic and harbored eosinophilic cytoplasm and hyperchromatic nuclei (c). A meshwork of fine fibers was observed in the acellular area, and cells with eosinophilic granular inclusions or hyaline bodies were observed (d). Lipofuscin granules showed various colors, from faint pinkish to dark brown (e). f, g Hyalinization was diffusely observed in the wall of the blood vessels and intra-tumoral matrix. h Scattered Rosenthal fibers were observed in the cerebellum surrounding the tumor. i-l Representative images of immunohistochemical analyses. Tumor cells were diffusely positive for S-100 protein (i) and focally positive for glial fibrillary acidic protein (j). Tumor cells were negative for Olig2 (k). The Ki-67 labeling index was less than 1% (l). Scale bars: 1 mm (a), 200 μm (b, g), 100 μm (f, h-j), and 50 μm (c-e, k, l)

Fig. 4

Flow diagram of systematic literature review