Primary mediastinal germ cell tumor with intratubular germ cell neoplasia of the testis--further support for germ cell origin of these tumors

Hailemariam et al.1 described the simultaneous occurrence of a mediastinal germ cell tumor and intratubular germ cell neoplasia in the testis in a patient age 32 years. They postulated that both lesions originated in a common germ cell source. A germ cell line can certainly give rise to two different germ cell neoplasms. This explanation was actually offered to account for the association between hematopoietic malignancy and mediastinal germ cell tumor in the same host.2 Other examples of somatic neoplasms arising in patients with germ cell tumors abound.3, 4 In fact, to carry this hypothesis even further back on the histogenesis pathway, it is possible that all multiple tumors occurring in a given patient, be they simultaneous or metachronous, represent different neoplastic manifestations of a pluripotent stem cell element, be the element germ cell3 or otherwise.5 Had the young patient survived the mediastinal germ cell tumor, he may indeed have been at increased risk of developing malignancies other than the tumor of the left testis. The specific type of subsequent cancer may depend partly on alterations in the microenvironment that is "bathing" the stem cell in question.6 In fact, changes in the cellular milieu caused by irradiation6 and/or chemotherapeutic agents3 may explain the occurrence of treatment-related cancers in general. It is important, however, to point out that despite advances in molecular genetics, we are not quite able to delineate, clearly, the clonality of cells within a single tumor,7, 8 let alone track genetic changes that can occur during the progression, including metastasis9, 10 and recurrence,11 of a given tumor; and we are even less prepared to track such changes in different tumors arising in the same patient. K. C. Lee M.D.*