Choristoma is a tumor-like mass that has lost continuity with the original normal tissue and develops in an ectopic position for some reason. In particular, osteocartilaginous choristomas containing normal cartilage and bone tissue are extremely rare, and no cases of osteocartilaginous choristoma developing in the lower lip have been reported. We describe a 68-year-old woman who had been referred to our clinic because of a painless mass in the right lower lip. Macroscopic examination revealed a submucosal mass lesion with a well-defined border and measuring approximately 24× 21× 19 mm. It was a pedunculated, movable, elastic hard mass. Magnetic resonance imaging (MRI) showed a well-defined mass above the orbicularis oris muscle. The lesion showed regions of isointense signal intensity with spots of high signal intensity on T1-weighted images and low signal intensity with heterogeneous areas of high signal intensity on T2-weighted images. A pleomorphic adenoma of the lower lip was diagnosed on the basis of clinical course, clinical findings, and MRI findings. Surgical excision (excisional biopsy) of the tumor was performed with the patient under general anesthesia. Histopathological examination led to the definitive diagnosis of an osteocartilaginous choristoma. No signs of recurrence have been noted as of 3 years after surgery.
