The patient went on to have endoscopic resection of the mass.
Histology
MICROSCOPIC DESCRIPTION: Serial sections show a small fragment of glial tissue which incorporates a slit-like space. This is lined by a more compact layer of glial tissue staining strongly for GFAP but with focal staining for epithelial membrane antigen. Scattered single siderophages are noted in tissue adjacent to the space and there are also scattered Rosenthal fibres. No evidence of tumour is seen. No pineal parenchymal tissue is identified. The features are of pineal cyst/pineal glial cyst.
FINAL DIAGNOSIS: Pineal cyst