Biology of metastases and its clinical implications: testicular germ-cell tumors.

This article deals with observations of the clinical behavior of metastatic germ cell cancers of testicular origin. Therefore, when we speak of biology of metastases, we refer to that seen by the clinician as opposed to the laboratory scientist. First, we will review our experience with chemotherapy for metastatic disease. From this we can gain insight into risk factors for relapse and survival. Furthermore, we can infer there are fundamental differences in the biology of germ cell cancers of testicular origin as opposed to primary mediastinal or primary retroperitoneal origin. Some of these differences are further discussed. We also identify "good risk" parameters and suggest criteria for expectant or conservative management postchemotherapy instead of postchemotherapy surgical management. Second, the diversity of metastases as evidenced by a wide histologic spectrum, is discussed in clinical terms. Among topics discussed are non-germ-cell malignant elements found within metastatic germ cell tumors, and possible mechanisms for their emergence. Third, the increasing awareness of long delayed, late relapse and its relative refractoriness to chemotherapy gives further insight into the clinical biology of metastatic germ cell cancer. The multipotential nature of the germ cell results in a wide variety of metastatic subtypes, each with its own clinical behavior. Therefore, a variety of clinical management strategies may be required based upon these different clinical behaviors.