Osteosarcoma is the second most frequent malignant bone tumour after multipl myeloma. Peak age is the second decade. Adolescents with severe pain occuring near a major joint such as knee should be regarded as having osteosarcoma unless proven otherwise. In such a condition, two plane plain X-ray and necessary imaging should be undertaken. Definitive diagnosis would be reached by biopsy. CT guided cutting nail biopsy or incisional biopsy should be performed on the planned incision line. Neoadjuvant chemotheraphy and subsequent limb salvage surgery is the preferred treatment method. Low necrosis rate, local recurrence, contaminated surgical margin are the negative prognostic factors. Five years of disease free survival with multidiciplinary approach is 65%. Patients should be followed up at least five years for probable systemic metastasis. The most predictive factors of treatment are chemotheraphy response of the tumour, and tumour free margins provided by wide resection besides early diagnosis and low tumour volume. Metastasectomy should be regarded in the presence and progression of lung metastasis.

Malignant fibrous histiocytoma of bone is a rare malignant tumor of bone consisted of collagen forming indifferentiated spindle cells. It may be regarded as a bony variant of malignant fibrous histiocytoma of soft tissues. Malignant fibrous histiocytoma of bone has been classified as undifferantiated high grade pleomorphic sarcoma in the last WHO classification. It may be primary or secondary. Clinical behaviour represents osteosarcoma and treated by means of osteosarcoma treatment. Neoadjuvant chemotherapy and limb salvage surgery, local wide excision and reconstruction is the preferred method of treatment.