Osteosarcoma of maxilla with unusual image findings in child.

Osteosarcoma of the head and neck is relatively rare and accounts for less than 10 percent of all osteosarcomas in general. We report a case of osteosarcoma in which imaging and histopathology of the hard palate of an 11-year-old boy yielded atypical findings. An approximately 8×15mm lesion found in the center of the palate was hard and healthy in color. Subsequent biopsy resulted in a diagnosis of nonepithelial malignant tumor. No abnormalities were observed in the maxillary bone or tooth on panoramic or occlusal radiographs. Computed tomography images revealed a mass lesion approximately 7×9×9mm in size on the hard palate extending into the maxilla. The cortex of the maxilla adjacent to the lesion was unclear in parts. The internal structures were slightly inhomogeneous and its density was lower than that of muscle. On magnetic resonance images, the lesion was represented by low signal intensity on T1-weighted (T1W) images and high signal intensity on T2-weighted images with fat-suppression. The margin of the lesion was a little unclear and the internal structures were slightly inhomogeneous. The lesion was enhanced homogeneously on post-contrast T1W images with fat-suppression. The histopathological diagnosis was fibrogenesis-type osteosarcoma. No findings specific to osteosarcoma such as localized enlargement of the periodontal ligament space alongside the root, cortical destruction, periosteal ossification or osteogenesis were found in this case.