Ossified spinal epidermoid cyst: A systematic review and case report.

Background: Epidermoid cysts (ECs) are rare, benign lesions which comprise less than 1 % of all spinal tumors. Calcification of spinal ECs is rare, and EC ossification within the lumbar spine has never been documented. We report the only known congenital lumbar epidermoid tumor with ossification and a literature review of intradural lumbar ECs. Methods: Studies meeting the following criteria were included: 1) EC as the primary tumor type, 2) intradural location, 3) involvement of the lumbar spinal level, and 4) primary presentation. Studies lacking individual patient data or published in a non-English language were excluded. Results: A total of 172 studies were reviewed and 43 were included in analysis. Of the 83 total patients, 37 (45.1 %) were male and 45 (54.9 %) female, at an average age of 26 years. The L3 and L4 spinal levels were most frequently involved. Acquired etiology was reported in 49 (59.0 %) patients, and 24 (28.9 %) cases were congenital. Multivariate analyses demonstrated trends between decreased age and improved outcome, decreased delay in diagnosis and improved outcome, and increased extent of resection with reduced recurrence. Nine calcified spinal ECs were identified, with no previous report of EC ossification in the lumbar spine. Conclusion: We present a case report of the only known ossified epidermoid tumor of the lumbar spine and a comprehensive literature review of 83 patients with intradural lumbar ECs. This review demonstrated trends between reduced age and improved outcome, reduced delay in diagnosis and improved outcome, and increased extent of resection with reduced recurrence.