MACROSCOPIC DESCRIPTION: An opened cyst 14 mm in diameter. The wall is composed of a thin dark fawn membrane and has a roughened inner surface. Separate fragment of soft fawn tissue up to 3 mm included.
MICROSCOPIC DESCRIPTION: The sections include tissue from normal pineal gland with glandular structures and rosettes divided by thin connective tissue membranes and the presence of corpora arenacea are noted. The cyst noted macroscopically appears to be lined by glial cells and compressed pineal gland parenchyma. There are scattered Rosenthal fibres and refractile brown pigment consistent with hemosiderin. The topoisomerase index is 1%. IDH-1 immunostain is negative.
FINAL DIAGNOSIS: Pineal cyst