Intraventricular meningioma - third ventricle

Although the histology is atypical for meningioma (see below), theThe patient has remained well 5 years after resection without evidence ofwent on to have a systemic malignancyresection.

Histology

Paraffin sections show a densely hypercellular spindle cell tumour. Tumour cells have mildly pleomorphic elongated vesicular nuclei and coarse bipolar processes and are arranged in intersecting fasciculi. A very occasional mitotic figure is identified. No necrosis is seen. No brain parenchymal tissue is included.

Very weak immunostaining for epithelial membrane antigen (EMA) is noted in tumour cells in some areas. Approximately 2-3% of tumour cells show strong nuclear staining for Ki-67. No immunostaining for cytokeratins (AE1/AE3, CAM 5.2; CK 7, CK 20), S-100 protein, GFAP, neurofilament protein, CD34, tyrosinase or smooth muscle actin (SMA) is seen in tumour cells.

Final diagnosis:

Third ventricle tumour: Undifferentiated spindle cell tumour of uncertain malignant potential.

Comment: 

Although the regional weak immunostaining for epithelial membrane antigen (EMA) in this tumour is consistent with meningioma, the histological appearances of tumour cells and their architectural arrangement are unusual for meningioma and are more suggestive of a mesenchymal tumour. Metastasis from a low grade sarcoma or gastro-intestinal stromal tumour (GIST) cannot be excluded.

Intraventricular meningiomaSelected images demonstrate a well circumscribed intraventricular mass near the foramina of Munro. It is isointense to grey matter on T1, hyperintense on T2 and demonstrates very vivid contrast enhancement. DWI demonstrate increased signal, however whether this represents T2 shine through or true diffusion restriction is uncertain. Obstructive hydrocephalus is present.