Intradiploic dermoid cyst of the lateral frontotemporal skull: case report and review of the literature.

Background: Intradiploic dermoid cysts represent 0.04-0.7% of cranial tumors. Fewer than 20 cases of dermoid cysts occurring in the lateral frontotemporal region with a sinus tract and bony involvement are described, only 7 with intracranial extension. We present the first report of such a lesion arising within the lateral coronal suture. As the literature on this topic grows, the matter of preoperative imaging for soft tissue and bony lesions of the lateral frontotemporal region is evolving, and this report offers a preliminary set of criteria for when imaging is a necessity. Case Report: A 2-year-old male presented with a bony lesion in the right frontotemporal region. Since birth the lesion had grown commensurately with the patient. Examination revealed an immobile hard mass overlying the right coronal suture with no discernable abnormality. Computed tomography demonstrated a cystic lesion without evidence of intracranial extension. Intraoperatively, the exophytic lesion was fully enclosed by bony matrix, interrupting the coronal suture as it approached the pterion. Following resection, pathology revealed an intradiploic dermoid cyst. Conclusion: Intradiploic dermoid cysts occurring within patent cranial sutures away from the midline are rarely described lesions. Complete surgical resection with careful follow-up is the treatment of choice.