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[Staging of osteosarcoma with skip metastases].

We reviewed the cases of 23 patients with histologically proven primary osteosarcoma of bone and histologically proven "skip" metastases. The patient had a Stage IIB (Enneking et al., 1986) lesion with interruption of the cortex and soft tissue extension. All 23 patients were treated by surgical resection of the primary lesion; 11 patients received either pre- and/or postoperative adjunctive therapy. Of the 23 patients one was alive and free of disease after a follow-up of 60 months: 22 patients had either a local recurrence or distant metastases within 16 months postoperative. We compared clinical course of these patients with 224 Stage II patients without a "skip" lesion and 31 osteosarcomas with lung and/or skeletal metastases (Stage III) at time of diagnosis. The disease-free interval and long-term survival in Stage II patients with "skips" was significant lower than those without identifiable "skips". The overall survival of those with "skips" was comparable of the survival rate of Stage III patients. Based on this small series, we concluded that patients with "skip" metastases should be staged as Stage III lesions and they should be excluded form ongoing therapy trials.