Epidermoid Cyst of the Buccal Mucosa Diagnosed by Magnetic Resonance Imaging and Ultrasonography: A Case Report and Review of the Literature

Objective: Epidermoid cysts are rare lesions in the oral cavity. Intraoral epidermoid cysts are most commonly located in the floor of the mouth; they are less common in the lips and buccal mucosa. Cysts arising from the buccal mucosa are often difficult to distinguish from other lesions. We herein report a case of epidermoid cyst in the buccal mucosa diagnosed with imaging. Methods: A 65-year-old Japanese man presented with a painless soft mass in the left buccal mucosa. MRI and ultrasonography were used to diagnose the mass correctly. Results: The well-circumscribed mass was covered with healthy buccal mucosa. The lesion showed low intensity in T1and high intensity in T2-weighted magnetic resonance imaging. The intensity did not decrease in fat-suppressed T2-weighted images. The interior of the lesion was homogeneous. Ultrasonography revealed a well circumscribed lesion with a heterogeneous interior. Surgical excision via an intraoral approach was performed under general anesthesia. Histopathology revealed that the cyst wall was lined with stratified squamous epithelium. The cystic cavity was filled with laminated keratin. Skin adnexa were not observed in the cyst wall. Based on histopathological findings, the lesion was diagnosed as an epidermoid cyst. No recurrence or other adverse events were observed in 6-month follow-up. Conclusion: The combination of MRI and US can be useful to diagnose dermoid cysts and epidermoid cysts.