I am honored to have been invited to write a foreword for this book, because tumors of the yolk sac have been a preoccupation of mine since the days of my residency, now more than 3 decades ago. At that time, a 3-year-old boy died of a testicular cancer of unknown histo genesis. It was bad enough that the child died, but it bothered me even more that medical science did not know the histogenesis of the tumor that destroyed him, and I decided to study testicular cancer. For re search training I sought out F. J. Dixon, who had written the Armed Forces Fascicle on testicular tumors. Dr. Dixon and I showed that embryonal carcinoma was a multipoten tial malignant stem cell that differentiated into the three embryonic germ layers of murine teratocarcinoma. This led to the idea that the normal counterpart of embryonal carcinoma must also be multi potent, and we focused on the preimplantation embryo for the histo genesis of the tumor. This idea was strengthened by the discovery that embryonal carcinoma cells made embryoid bodies in the ascites and it was possible to observe the development of these bodies in vitro. These observations led to the idea that embryonal carcinoma was a caricature (gross misrepresentation) of early development, and car cinomas in general were a caricature of the process of renewal of their normal counterpart.

1. Comparative Development of the Mammalian Yolk Sac

2. Development of the Human Yolk Sac
3. Histology of the Secondary Human Yolk Sac with Special Reference to Hematopoiesis
4. Kinetics of Hematopoiesis in the Human Yolk Sac
5. Macrophages in the Human Yolk Sac
6. ?-Fetoprotein and Other Proteins in the Human Yolk Sac
7. Yolk Sac Abnormalities: A Clinical Review
8. Experimental Models of Injury in the Mammalian Yolk Sac
9. Ultrasonography of the Human Yolk Sac
10. Morphological Changes of the Secondary Human Yolk Sac in Early Pregnancy Wastage
11. Yolk Sac Carcinoma: History of the Concept and the Experimental Models
12. Immunohistochemical Markers of Yolk Sac Tumors
13. Pathology of Ovarian Yolk Sac Tumors
14. Clinical Features and Management of Gynecologic Yolk Sac Tumors
15. Pathology of Testicular Yolk Sac Tumors
16. Pathology of Extragonadal Yolk Sac Tumors
17. Unusual Patterns, Subtypes, and Differential Diagnosis of Gonadal Yolk Sac Tumors
18. Clinical Features and Management of Testicular and Extragonadal Yolk Sac Tumors.