en Surgery Surgery case report case report Osteosarcoma is relatively rare in the jaws and variable in presentation, thus its recognition may be quite confusing and delay diagnosis and treatment. Also, in contrast to most malignancies, osteosarcoma is usually encountered earlier in life and may clinically resemble features of more common oral entities such as chronic osteomyelitis, fibrous dysplasia, osteoblastic metastatic carcinoma, ossifying subperiosteal hematoma and chondrosarcoma. Hence definitive treatment may be inadvertently delayed, jeopardizing the chance for cure. A case of chondroblastic osteosarcoma of the mandible which was mistakenly treated as a pericoronal infection by a dentist is presented. The treatment instituted was continued for several weeks despite progression of the lesion, after which the patient was referred. This delay made necessary a more radical resection than that which would have been needed had the patient been referred earlier. 271 275 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-572&slc_lang=en&sid=1 MOHAMMAD HOSEIN KALANTAR MOTAMEDI 20031947532846006009 20031947532846006009 Yes From the Department of Oral. Maxillofacial and Reconstructive Surgery, Baqiyatollah Hospital, Imam Hosein University Of Medical Sciences, Tehran, I.R. Iran. MOHAMMAD HASAN KALANTAR MOTAMEDI 20031947532846006010 20031947532846006010 No MOHAMMAD REZA KALANTAR MOTAMEDI 20031947532846006011 20031947532846006011 No ISMAIL YAZDI 20031947532846006012 20031947532846006012 No