No abstract

The discovery of 2 yolk sac carcinomas of the mouse has established a basis in comparative pathology for the occurrence of this type of tumor in other species with yolk sacs. Grafts and tissue cultures of extra‐embryonic yolk sac of the mouse have developed a clear understanding of the types of tissues one might expect in yolk sac carcinomas. The morphological appearance, age of incidence, and natural history of yolk sac carcinomas of the testis of boys have been compared to those of embryonal carcinomas. The prognosis for boys under 2 years of age with this tumor is astonishingly favorable, but that for boys over 2 years of age is desperately bad. An elderly man with the disease developed metastases soon after treatment. It is clear that yolk sac carcinoma is an entity deserving incorporation in the classification of testicular tumors as suggested by Teilum.