Intradiploic primary epithelial inclusion cyst of the skull.

Intradiploic inclusion cyst of the skull presenting as a calvarial defect is fairly uncommon in the neuroscience practice. They are benign in nature, slow to grow, and clinically difficult to differentiate from other causes of calvarial defects. We present a case of a healthy 55-year-old woman who presented clinically for an asymptomatic lump over the right parieto-occipital region of the scalp of 4-month duration. The radiological features were suggestive of presence of a large intradiploic solitary cyst and additional multiple lytic defects with sclerotic borders, destroying the underlying bone. The gross and histomorphological features of the right parieto-occipital craniectomy specimen received were pathognomic of an intradiploic primary epithelial inclusion cyst of the skull bone. The importance of its benign nature, embryogenic origin, and differentiation from other cystic lesions with similar histology is stressed. We report this case for its unique histomorphology and first of its kind in the Indian literature.