Malignant transformation of an intracranial epidermoid cyst 25 years after initial surgery: a case report and systematic review.

We report a rare case of delayed malignant transformation of an intracranial EDC to SCC, occurring nearly 25 years after initial resection. Transformation time in the no-surgery group was statistically significantly shorter as compared to the surgery only and surgery + adjuvant therapy groups. OS was statistically significantly higher in the surgery + adjuvant therapy group as compared to the surgery only and no surgery groups.