The patient went on to have a posterior fossa (sub-tentorial) craniotomy and resection of this tumour.
Histology
The sections show multiple fragments of tumour, some associated with a densely fibrous membrane consistent with dura mater. The tumour shows a variety of growth patterns, including fascicular areas, areas with abundant collagenous fibrous tissue between cells and foci of whorl formation. A very occasional psammoma body is noted. Individual tumour cells are elongate, with fairly abundant eosinophilic cytoplasm, often with poorly circumscribed cytoplasmic outlines. Nuclei are generally rounded or oval, with finely granular nucleoplasm, sometimes with cytoplasmic inclusions.
There are areas of the tumour where cellularity is high, with large crowded nuclei and cells with raised nuclear to cytoplasmic ratio. In such areas, the mitotic count is up to 10 per 10HPF. The features are those of a meningioma, WHO grade 2. No cerebral tissue is recognised and no comment can be made about cerebral invasion.
FINAL DIAGNOSIS: Pineal region tumour - meningioma, WHO grade 2.