Intradiploic epidermoid cyst in the skull: Case report and systematic review.

Intradiploic epidermoid cysts are rare, benign tumors, accounting for less than 1% of all intracranial tumors. Due to their scarcity, we are reporting a case of an intradiploic epidermoid cyst and reviewing several similar cases in the literature to provide a better description of this tumor and analyze its clinical and radiological features. We conducted a search on the PubMed database for studies published between January 2010 and February 2023, including studies of nontraumatic and noniatrogenic calvarial cysts. We found a total of 34 studies and 41 patients, with an average patient age of 42.5 years. Common symptoms included painless masses, headaches, and seizures. The occipital, frontal, and parietal regions were the most common locations for these tumors. Some patients experienced complications such as otitis media, infection, or extension into the orbit and brain. Surgical resection was performed in all cases except for 2 patients with contraindications to surgery. Histological examination confirmed the diagnosis of an intradiploic epidermoid cyst. These cysts are rare skull lesions and can potentially cause neurological deficits due to their mass effect. If incompletely resected, they may also undergo malignant transformation. No single institution has accumulated enough cases to describe this rare tumor accurately. Therefore, through this review, we aim to highlight this tumor's epidemiological, clinical, and radiological features.