Giant Intradiploic Epidermoid Cyst of the Occipital Bone with Posterior Fossa Compression: A Case Report

Background Intradiploic epidermoid cysts are rare lesions that account for a small fraction of intracranial tumors with occasional malignant transformation. Occipital involvement is particularly uncommon, and lesions may reach giant dimensions with a risk fossa compression.Case Presentation A 60-year-old woman presented with a 12-month history of progressive headache and vertigo. Magnetic resonance imaging (MRI) revealed a large, diffusion-restricting extra-axial mass arising from the occipital bone and extending into the posterior fossa. She underwent a posterior fossa craniotomy with gross-total resection while preserving dural integrity. Histopathology confirmed an epidermoid cyst. The postoperative course was uneventful, and follow-up MRI showed complete resection with no recurrence.Conclusion Giant intradiploic epidermoid cysts of the occipital bone, though histologically benign, can cause extensive bone destruction and significant posterior fossa mass effect. Accurate preoperative imaging and meticulous surgical planning are critical to achieving safe gross-total excision and favorable outcomes, particularly in atypical or extensive presentations.