Epidermoid cysts measuring up to 3 cm in diameter account for more than 80% of all epidermoid cysts. Large epidermoid cysts are often accompanied by oral dysfunction. We report the case of a 60-year-old man with a large sublingual epidermoid cyst accompanied by articulatory disorder and sleep apnea. The patient presented with a chief complaint of swelling extending from the floor of the oral cavity to the submental region. On examination, a soft, well-circumscribed mass was observed. Computed tomography and magnetic resonance imaging revealed expansion into the sublingual space. The tongue was displaced backward, and the airway was narrowed. An articulatory disorder was revealed by a speech test, and severe sleep apnea was detected on polysomnography (apnea hypopnea index, 45.8). An epidermoid or dermoid cyst was diagnosed on the basis of turbid fluid contents obtained by puncture. The mass was surgically resected, and histopathological examination confirmed an epidermoid cyst. A postoperative speech test and polysomnography revealed significant improvement. The findings from this case suggest that dysfunction should be considered in patients presenting with a large mass bulging outward in the oral cavity, even if the patient is asymptomatic.
