Background: Intradiploic dermoid cysts represent 0.04– 0.7% of cranial tumours. Very few cases of dermoid cysts occurring in the lateral front temporal region with a sinus tract up to dura are described in literature. We hereby report a case with intradiploic dermoid cyst with intracranial (but extra parenchymal) extension with complaint of a discharging sinus since birth. Case Report: A 2 year old male presented with history of serous discharge from the sinus located in right lateral frontal region at the level of coronal suture noticed since the age of two months. On CT and MRI imaging of brain, patient was found to have intradiploic expansile lytic lesion in the region corresponding to the sinus and was extending intracranially. Differential diagnosis as per imaging studies were Dermoid cyst, Epidermoid cyst and Eosinophilic granuloma. Gross total excision of the cyst along with involved sinus tract done and histopathology of the cyst confirmed it to be Dermoid cyst. Conclusion: Intradiploic dermoid cysts are relatively rare especially with discharging sinus and intracranial extension. We hereby add one such rare case to the literature. Surgical excision with careful excision of tract forms the adequate treatment of choice.

Keywords: Dermoid; Sinus.