Histology and biology of metastatic chondroblastoma. Report of a case with a review of the literature.

This case report of a metastasizing chondroblastoma with a review of the literature was undertaken to gain a better understanding of the biologic behavior of this exceedingly rare tumor and thus to facilitate its clinical management. The lung was by far the most frequent metastatic site. Thus, all 7 patients with a proven metastatic chondroblastoma recorded up to now including the present case had developed multiple pulmonary metastases. The interval between the initial diagnosis of the primary and manifestation of lung metastases proved to be long, with a mean of 8.4 years. The average survival time was at least 12.3 years. The mean interval between diagnosis of metastatic disease and death amounted to at least 6.3 years. The histomorphologic features of metastatic chondroblastoma, its local recurrences and of the metastatic lesions differed in no way from conventional chondroblastomas. Because of the lack of cellular criteria of malignancy it is impossible to predict the potential biologic behavior of chondroblastomas, in particular with respect to their ability to metastasize. However, the presence of tumor emboli in the primary lesion is highly suggestive of a subsequent development of metastatic disease. The delayed induction of hematogenous metastases is best explained by a limited growth potential of the tumor cells. In case of a large primary tumor--especially in flat bones--with soft tissue invasion or in the presence of tumor emboli an aggressive surgical approach is suggested. When lung metastases have developed their surgical removal is recommended to hopefully prolong live expectancy or even to obtain a curative effect.