We report a patient with a metastatic osteosarcoma of the gingival region, which was treated with chemotherapy and additional interferon therapy. The patient was a 13-year-old boy with an osteosarocoma of the left proximal humerus. After amputation, he was treated with high-dose MTX therapy as an adjuvant chemotherapy. Two years later, the patient had the gingival metastasis. Rapid growth of the tumor prevented him from receiving surgical treatment. After admission, he underwent the treatment with i. m. injections of HLBI (human lymphoblast interferon), and also with ADM chemotherapy. At first, the dose of HLBI was 3×106 IU per day, and gradually increased. Finally, the total dosage of HLBI reached 760.5×106 IU. A transient suppressive effect for tumor growth was seen in the first period of this treatment. However, the metastatic mass had increased in size during the treatment until death, three month after admission. The pathological diagnosis of the primary lesion was chondroblastic osteosarcoma, but histologic examination of the metastatic lesion showed chondrosarcomatous change after this treatment.
