[A Case of Right Frontal Dermoid Cyst with Temporal Imaging Changes in the Desease Course].

Dermoid cysts are rare benign intracranial neoplasms derived from embryonal remnant tissues. Here, we describe a case of dermoid cyst located in the right frontal lobe, which showed repeated changes on CT. An 11-year-old girl was referred to our hospital to treat a brain neoplasm. Brain CT and MRI revealed a cystic tumor in the right frontal lobe. Incidentally, brain CT had been performed 6, 2, and 1 year before the presentation, which demonstrated repeated changes in the tumor over the clinical course. Gross total resection of the tumor was achieved through right frontal craniotomy. Histological findings revealed keratin flakes, mature bones, cholesterol crystals, and granulation with macrophages. The cyst wall was composed of squamous epithelium with adnexal structures, such as hair follicles and sebaceous glands. Therefore, we diagnosed the tumor as a dermoid cyst. The postoperative course was uneventful, and she was discharged on postoperative day 10 without neurological deficits. Dermoid cysts are difficult to be diagnosed on routine neuroimaging. An accurate diagnosis requires details of the clinical course and analysis of both imaging and pathological studies.