Well-differentiated intraosseous osteosarcoma of the jaws: experience of two cases from the Instituto Nacional de Cancerología, México.

Osteosarcomas of the jaws represent less than 10% of all osteosarcomas, and most of them are high-grade neoplasms. Prognostic factors in overall survival include tumor size, location and histologic grade. Examples of well-differentiated (low-grade) intraosseous osteosarcomas of the jaws (WDIOJ) have been rarely reported. This article presents two cases of this unusual lesion, one of which was located in the maxilla of a 17-year-old man and the other developed in the mandible of a 37-year-old woman. CT scan was necessary to detect the small foci of penetration into the thinned cortical bone and the reactive periosteal bone formation, which are important findings to establish the correct diagnosis of WDIOJ and help to exclude other benign intraosseous lesions that may be very similar histologically, such as fibrous dysplasia, ossifying and desmoplastic fibromas. In spite of tumor size (mean 5.2 cm), their well-demarcated borders allowed complete removal of both tumors. There is no evidence of tumoral activity in any of our patients after follow-up periods of 15 months and 5 years. Wide excision seems to be the treatment of choice for this subgroup of osteosarcomas.