The evolution of mature teratoma from malignant testicular tumors.

During the period of 1969--1976, twelve cases of malignant germ cell tumor of the testis were seen in which the diagnosis was associated with the subsequent development of one or more metastases composed histologically of fully mature teratoma. These patients had a variety of primary germ cell tumors in the testis and were treated with radiation therapy and/or chemotherapy in addition to surgery, prior to the development of mature teratomas in different anatomic sites. The development of mature teratoma in this clinical setting seems to be a favorable prognostic sign, inasmuch as only one of the 12 patients has died with known persistent cancer. Since the incidence of this phenomenon seems to be increasing, the mechanism is probably related, directly or indirectly, to therapy.