Multifocal osteosarcoma is an uncommon and aggressive presentation of osteosarcoma.
Case report: We report a case of multifocal osteosarcoma in a 12-year-old boy who was admitted for a tumor of the skull, associated with pleural and pulmonary nodules. A computed tomography scan of the head showed a calcified lesion with intra- and extracranial extent. A biopsy of the skull tumor showed an osteoblastic osteosarcoma. Three weeks later, the patient developed two other tumors of the skull, a tumor of the left shoulder and a pelvic pain. Radiographic studies confirmed the presence of further lytic lesions at these sites. The patient was unresponsive to chemotherapy (high dose methotrexate and doxorubicin) and died nine months later.
Comments: Multifocal osteosarcoma, or osteosarcomatosis, is a highly aggressive form of osteosarcoma. The multiple lesions can all arise synchronously as primary tumors, or appear to be one dominant site with early and rapid appearance of secondary lesions. The incidence is reported to be between 1 and 10% of osteosarcoma. The histology shows an osteosarcoma of osteoblastic type in most cases.
Conclusion: Despite intensive chemotherapy, the prognosis remains poor. The debate remains as to whether or not this clinical presentation represents true multifocality of the disease or a relatively unusual metastatic pattern of osteosarcoma.