We present a case of dermoid cyst of the temporal bone of a 3-year-old Japanese female. The mother of the patient noticed the tumor of the left temporal bone at 1 year and 2 months old. When we first saw the patient, there was a hard, immobile subcutaneous tumor on the left temple, which existed between external and internal laminas of the left temporal bone with a partial bone defect on the CT image. Under general anesthesia, we made a transversal excision above the tumor, divided the temporal muscle according to its fiber, and reached the surface of the tumor. The superior 2/3 of the tumor was covered with bone and the inferior 1/3 was not covered with bone. The pedicle of the tumor came directly from the dura mater. The pedicle was tapered off and was easily removed form the temporal bone defect with the open dura mater. The bone around the tumor was flattened, and the fascia, dermis, and epidermis were sutured respectively. The pathological test shows dermoid cyst. Dermoid cyst frequently develops subcutaneously and rarely develops from cranial bones. There has been no case report of a dermoid cyst developing from cranial bones without destroying the bones.
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