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.

• 김정헌(연세대학교 치과대학 구강악안면외과학교실) | Junghun Kim (Department of Oral & Maxillofacial Surgery, Yonsei University College of Dentistry)
• 한다울(연세대학교 치과대학 구강병리학교실) | Dawool Han (Department of Oral Pathology, Yonsei University College of Dentistry)
• 김동욱(연세대학교 치과대학 구강악안면외과학교실) | Dongwook Kim (Department of Oral & Maxillofacial Surgery, Yonsei University College of Dentistry) Correspondence