Disparate histologic responses in simultaneously resected primary and metastatic osteosarcoma following intravenous neoadjuvant chemotherapy.

Seven patients with newly diagnosed metastatic osteosarcoma underwent simultaneous resection of the primary tumor and metastases following intravenous (IV) neoadjuvant chemotherapy. Histologic response was assessed in all tumor specimens. Disparate responses were noted between primary tumor and metastases and, in some cases, between two or more metastatic tumor deposits. The diverse histologic response to neoadjuvant chemotherapy suggests tumor cell heterogeneity. Changing postoperative therapy on the basis of the histologic response induced in the primary tumor may not be appropriate.