Extraskeletal Osteosarcoma Case Report And Literature Review

Extraskeletal osteosarcoma (EOS) is a rare malignant soft tissue sarcoma. It accounts for about 1.2% of all soft tissue sarcomas; 3.7%-4.6% of all osteosarcomas. Most patients have local recurrence or metastasis, or both . The lung is the most common site of metastasis. EOS is a very aggressive tumor with a relatively poor prognosis, the 5-year survival rate is 25%-38%, its median survival time is only 8 months after metastasis. The patients with EOS are mostly older than 40, the mean age of patients is 50.7-54.6. The most common location of EOS is the lower extremity, followed by the upper extremity and the retroperitoneum, the trunk, hand, pleura are reported. The pathogenesis of EOS is unclear, from the issues: a history of trauma has been reported in 12%-30% of patients; 5.5% of all has previous radiation therapy locally; a case of long term intramuscular injection also been reported and there are cases described in which EOS is presumed to be preceded by soft tissue sarcoma, such as myositis ossificans lesions. To be qualified as an EOS, the tumor must (1) arise in the soft tissue and not be attached to bone or periosteum, (2) have a uniform sarcomatous pattern ( to exclude the possibility of amixed malignant mesenchymal tumor), (3) produce osteoid and/or cartilage matrix. The EOS patients often have no pain or tenderness except for a gradually enlarging mass in soft tissue. The final diagnosis should be determined by pathologic evidence, microscopically, the tumors contained variable amounts of spindle cell stroma, osteoid and/or bone, and cartilage. The current multimodality theatment ofEOS is combined by limb-sparing surgery, radiotherapy and chemotherapy. Radical resection can descrease the number of patients with recurrence but have no remarkable impact on distant metastasis. Radiotherpy and chemotherapy play an adjuvant role in the treatment of EOS, improve the resection rate and reduce the recurrence and metastasis. Adjuvant radiotherapy is usually given to patients who have large lesions or after resection of local recurrence. The front-line regimen consisting doxorubicin is administered to late cases. It is useful to re-resect after recurrence or metastasis. The department once received a male patient, 36 years old. There was a painless, gradually enlarging mass in the end of his left thigh. After resection, it proved to be EOS with suffient pathologic evidence, and during the last 4 months, it reoccured twice in the same site with lung metastasis. The patient receiced intravenous chemotherapy twice and intraartery perfusion once after resection of recurrence. 1 year later, the patient died of respiratory dysfunction.