Sitting position to the posterior fossa approach with suboccipital craniectomy, with surgical exposure of a white mass prior to resection.
Histology
No malignant cells.
Cystic lesion with stratified, keratinising squamous epithelium with anucleated squames, with surrouding granulomatous reaction presumably due to rupture.
The Findings are consistent with epidermoid cyst.
Note, that one of the differentials is that of a neuroenteric cyst which have ciliated mucin-producing epithelium but can show squamous metaplasia. However, no anucleated squames or keratohyaline granules should be present, which are in this case.