A case of osteocartilaginous choristoma at the floor of the oral cavity

Osteocartilaginous choristomas are benign bone lesion composed of hyaline cartilage that undergo ossification and arise when osteochondral cells proliferate into surrounding tissues. In the oral and maxillofacial regions, these lesions usually occur on the dorsum of the tongue, with no reported cases of osteocartilaginous choristomas occurring on the oral floor. We report the case of a 57-year-old Japanese male referred to our hospital in late November 2021 with the chief complaint of tongue hypoaesthesia and a mass on the right side of the oral floor. Clinical examination revealed that the lesion was a 22 × 13 mm elastic hard mass with an ulcer at the centre of the lesion on the right side of the oral floor behind Walton's canal orifice. Computed tomography images showed an opaque mass with a major diameter of 20 mm, internal heterogeneity, and a well-defined border located slightly to the right of the floor of the oral cavity. Surgical resection was performed through an intraoral incision under local anaesthesia. The imaging and surgical findings at our hospital showed a 22 × 15 mm lesion with clear boundaries, which could be removed as a single mass from the surrounding connective tissue. Histological investigation revealed that lesion has the characteristics of hyaline cartilage with some areas showing ossification, leading to a diagnosis of osteocartilaginous choristoma of the oral floor. The patient has progressed well and remains recurrence-free 2 years postoperatively.