Germ cell tumours of childhood. Report of 170 cases including 59 pure and partial yolk-sac tumours.

170 germ cell tumours of childhood and adolescence were studied by light microscopy and immunohistochemistry. The male-to-female ratio was 1:1.3. 52 (30.6%) tumours were benign (mature teratoma), 30 (17.6%) potentially malignant (immature teratoma), and 88 (51.8%) unequivocally malignant. The main locations were ovary, testis and sacrococcygeal region. 92 tumours were located in a gonad, 78 tumours in extragonadal sites (ratio: 1.2:1). Of the frankly malignant tumours 40 were yolk-sac tumours (YST) and an additional 19 tumours of more than one histological type contained a YST component. Therefore, 67% of the malignant tumours had a YST component. Children with immature teratoma and pure YST showed the lowest median age (5 and 24 months, respectively), while children with germinomas of various locations had the highest median age (153 months). A festoon pattern was the predominant histological feature in all YST and in the YST component of mixed germ cell tumours. Hyaline globules were found in 33/37 YST and in 16/17 YST components. Immunohistochemically, alpha 1-fetoprotein (AFP) was demonstrated in 18/22 YST and in 6/7 YST components of mixed germ cell tumours. Hyaline globules were mostly AFP-negative (only 5 cases with AFP-positive globules in addition to many AFP-negative globules). In 3 cases beta-HCG-positive giant cells were seen. In most YST prekeratin intermediate filaments could be demonstrated in the epithelial cells. Follow-up data, available from 51 cases of YST and tumours with YST components showed disease-free survival in 37 cases (72.5%). 10 patients (19.6%) died of disease, and 4 patients (7.8%) are living with disease. The comparably high rate of survivors reflects the effectiveness of modern therapy, particularly polychemotherapy, in addition to surgery.