Generally, dermoid cysts commonly arise from the anus and ovaries. Oral and maxillofacial lesions are most commonly observed in the midline of the floor of the mouth, and lesions arising from the upper lip are relatively rare.
A 50-year-old man was referred to our hospital due to swelling of the left upper lip. Clinical examination revealed an elevated alar base, Gerber protrusion and nasal deformity. Ultrasonography revealed a clearly defined 30-mm lesion with more hypoechoic bands. Meanwhile, magnetic resonance imaging revealed a 30-mm mass below the orbicularis oris of the left upper lip. The lesion had a homogeneous, low-signal intensity on T1-weighted imaging. Thus, based on these findings, a dermoid cyst was suspected. The lesion was then removed en bloc without the overlying skin while the patient was under general anaesthesia. Histopathological examination revealed a cystic cavity lined by an orthokeratinised stratified squamous epithelium. However, skin appendages were not found. Based on the clinical and histopathological features of the lesion, a diagnosis of epidermoid cyst was made. Swelling of the left upper lip, nasal deformity and Gerber protrusion significantly improved after surgery.
Although dermoid cysts arising from the upper lip are rare, the diagnostic accuracy for dermoid cyst can be improved with the combined use of ultrasonography and other imaging modalities even though these lesions are difficult to distinguish from differential diagnosis.

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