Synchronous multicentric osteosarcoma: the case for metastases.

Objective: There is a current debate whether multicentric osteosarcoma represents synchronous multiple primary osteosarcomas or metastatic disease. The purpose of this report is to evaluate the etiology, presentation, and classification of this entity.

Design And Patients: Six patients ranging in age from 7 to 29 years were studied. The clinical, radiographic, and pathologic findings are reported. In addition, a review of the literature was undertaken.

Results: The clinical courses of our six patients as well as a review of the literature suggest that multicentric osteosarcoma represent one extreme of a continuous scale of metastatic osteosarcoma rather than multiple synchronous primary tumors. The presentation is unusual and the clinical behavior distinctive, but the mechanism of spread remains the same: blood-borne and lymphatic-borne.

Conclusions: Our experience with these six patients supports the concept in the recent literature that synchronous osteosarcoma is one extreme of the spectrum of metastatic osteosarcoma. Its unique features are: (1) multiple radiodense lesions that present simultaneously with or without pulmonary metastases; (2) a single "dominant" lesion with multiple smaller lesions; and (3) a uniformly rapid, fatal prognosis. Osteosarcoma should be regarded as a metastatic disease, even when only a single primary lesion is found at the initial presentation.