Meningioma with granulofilamentous inclusions

Pathology and molecular genetics of meningioma: recent advances

Meningiomas are the most common intracranial primary neoplasm in adults. Although the spectrum of clinical and molecular genetic issues regarding meningiomas remains undefined, novel genetic alterations that are associated with tumor morphology, malignancy, or location have recently been discovered. This review focuses on recent advances in understanding of the heterogenous pathology of meningiomas, particularly on associations between the clinical, histological, etiological, epidemiological, and molecular genetical aspects of the neoplasm.

Granulofilamentous meningioma

A 55-year old female was referred to the Department of Neurosurgery, Kitasato Hospital, because of a hearing impairment. Neuroimaging revealed a typical meningioma attached to the falx in the right frontal region. During surgery, an encapsulated, circumscribed, reddish-gray, slightly hard tumor attached to the falx was completely removed by an interhemispheric approach. On light microscopy, many of the tumor cells contained eosinophilic inclusions with single or multiple vacuoles that displaced the cytoplasm. The nuclei of the tumor cells were eccentric. There were no signs of malignancy in the specimen. Electron microscopy revealed that most of the eosinophilic inclusions were composed of filaments measuring 12 nm in diameter. There have been several reports of benign meningiomas with eosinophilic inclusions composed of intermediate filaments. The microscopic differences between these types of tumor and rhabdoid meningiomas are very subtle, and it is important the two types of tumors are not confused. Benign meningiomas with eosinophilic inclusions comprising intermediate filaments, for example the tumor described in this report, have been diagnosed as granulofilamentous meningiomas, which is a subtype of benign meningioma.

Pediatric embryonal tumor of the cerebellum with rhabdoid cells and novel intracytoplasmic inclusions: distinction from atypical teratoid/rhabdoid tumor

We report a case of embryonal tumor with novel inclusion bodies occurring in the cerebellum of a 12-year-old girl. The tumor was histopathologically composed of small undifferentiated cells intermingled with a small number of rhabdoid cells, which had an ultrastructural feature of intermediate filament whorls. Immunohistochemically, the neoplasm showed a polyphenotype, including glial fibrillary acidic protein (GFAP), S-100, synaptophysin, chromogranin A, cytokeratin, vimentin, smooth muscle actin, and desmin. However, epithelial membrane antigen (EMA) immunoreactivity was absent. The MIB-1 labeling index was high (25.6%). Ultrastructurally, there was no evidence of neuronal or myogenic differentiation. The small neoplastic cells contained numerous small intracytoplasmic inclusions stained pink by eosin and red by Masson's trichrome stain. The inclusion body was a densely packed, granulovesicular structure at the electron microscopic level, and was immunoreactive for vimentin, GFAP, desmin, and actin. Reverse transcription-PCR and immunohistochemistry showed the expression of INI1 at the RNA and protein levels, respectively. In conclusion, this tumor was differentiated from atypical teratoid/rhabdoid tumor by the absence of EMA and the presence of INI1 mRNA and protein, and diagnosed as an unclassified, embryonal tumor. Eosinophilic, granulovesicular inclusions of the tumor cells are novel cytoplasmic inclusions in the brain tumor.