A systematic review of clinical features of intradiploic epidermoid cysts and strategies for patient management.

Intradiploic epidermoid cysts (IECs) are rare cystic calvarial lesions. Due to their rarity, there is a clinical need to aggregate the collective experience reported in the literature to characterize typical clinical features, clinical predictors of patient outcomes, and management strategies used for this entity. Following PRI SMA guidelines, 127 patients from 94 studies (77 case reports, 17 case series) were included with individual patient data. Clinical data on demographics, clinical presentation, imaging features, management approaches, and outcomes were characterized, and predictors of outcome were evaluated. The cohort had a median age of 44 years (range = 18-81). Common presenting clinical features included headache (50%) and a palpable mass (48%), with half reporting antecedent head trauma. Lesions most frequently involved the occipital (28%), frontal (26%), and parietal bones (15%), with 13% localizing to multiple bones of the calvarium. Surgical resection was performed in all but one case, achieving a gross total resection (GTR) in 92% and complete cyst capsule removal in 87%. The rate of recurrence was significantly lower in those who received a GTR versus a subtotal resection (4% vs. 57%, p < 0.001) and in cases where the capsule was completely versus incompletely removed (2% vs. 66%, p < 0.001). IECs should be suspected in patients presenting with headaches or palpable skull masses with osteolytic non-enhancing and diffusion-restricting T2 hyperintense calvarial lesions. Complete surgical excision with total cyst capsule removal is the goal for IEC management. Close long-term monitoring remains essential, particularly in lesions that have been subtotally resected.