Encapsulation around malignant bone tumors after preoperative adjuvant treatment.

The effect of preoperative adjuvant treatment on encapsulation around the tumors was studied histologically in 16 patients with osteosarcoma and 2 patients with malignant fibrous histiocytoma of bone. The reactive zone in biopsy specimens was transformed into collagenous connective tissue after preoperative adjuvant treatment. The whole sections of specimens resected surgically from all 18 patients showed a thick capsule formation at the peri- and parosteal region of the tumors. However, no capsular structure was identified in the bone marrow. In skeletal muscles, the degree of encapsulation was correlated with the effect of preoperative adjuvant treatment. These results suggest that effective preoperative adjuvant treatment on malignant bone tumors clarifies the border between the tumors and the normal tissues in the extraosseous part, especially in the peri- and parosteal region.