High-Grade Conventional Osteosarcoma of the Mandible Associated With P53 Germline Mutation.

High-grade conventional osteosarcoma of the mandible is a rare entity that can manifest as a rapidly growing mass. The authors report the case of a young adult patient with right mandible pain and swelling and a history of humeral osteosarcoma treated over 1 decade earlier. Computed tomography and magnetic resonance imaging showed a mass arising from the right mandible that progressed despite induction chemotherapy and the patient underwent surgery. Histopathology revealed the presence of malignant osteoblasts and osteoid, which led to the diagnosis of high-grade conventional osteosarcoma. There were also regional lymph node metastases. Genetic testing revealed a p53 germline mutation. The presence of mandibular osteosarcoma in a young patient should raise the suspicion of an underlying p53 germline mutation. Ultimately, the recurrent tumor regressed with Etoposide and Ifosfamide.