A 20-year-old woman who had a main symptom of intermittent pain in both mandibular third molar visited our hospital. In CBCT findings, the #38, 48 teeth were located on the lingual side of the inferior alveolar nerve. In addition, a large stone about 12mm in length was observed in the right Wharton's duct in CBCT findings. Neck CT scan was performed and a large stone about 12mm in length was observed, and the accumulation of saliva in the rear of the stone was observed. The patient underwent sialolithotomy and #38, 48 tooth extraction through intraoral approach under general anesthesia. The removed stone was similar in shape and color to a tooth. The removed stone was markedly fragmented and composed of dentin and enamel-like tissue which showed lamellate arrangement in microscopic examination. Patient was presently symptom free after 10-months postoperatively.

Parosteal osteosarcoma, a subtype of juxtacortical osteosarcoma, has a better prognosis compared to central osteosarcoma with a relatively low risk for recurrence and metastasis. Rarely, it can arise synchronously with other malignant tumors. Synchronous malignancies are defined as the occurrence of a second primary malignancy within 6 months of the appearance of the first malignancy. Here in, we introduce a 64-year-old woman who visited the Department of Oral & Maxillofacial Surgery, Yonsei University Dental Hospital with a 2 year history of a whitish verrucous lesion on the palate. She presented an exophytic mass on mandible during the following visits. Histopathologic evaluation revealed a synchronous parosteal osteosarcoma and squamous cell on right mandible and a precancerous verrucous leukoplakia on the palate.