IMMATURE TERATOMAS IN CHILDREN - PATHOLOGICAL CONSIDERATIONS - A REPORT FROM THE COMBINED PEDIATRIC-ONCOLOGY-GROUP CHILDRENS CANCER GROUP

Pediatric germ cell tumors (n = 135) with a major component of immatur e teratoma (IT) registered on Pediatric Oncology Group/Children's Canc er Group treatment protocols from 1990 to 1995 were reviewed. Sixty ca ses were pure IT with no malignant component and 75 were mixed tumors with a major component of IT. Foci of yolk sac tumor (YST) were presen t in all 75 mixed tumors; additional malignant components were present in 15. The IT component was as follows: 47% grade 3, 29% grade 2, 24% grade 1. There were no significant correlations between tumor grade a nd patient age by specific subsets or overall (all p > 0.10). Signific ant correlations were detected between stage and the presence of foci of YST (p = 0.0145) and grade and the presence of foci of YST (p < 0.0 01). Serum a-fetoprotein concentrations were elevated at diagnosis in 96% of ovarian tumors with foci of YST and were mildly elevated (< 60 ng/dL) in only 16% of tumors without YST. Overall 2- to 6-year surviva l rare was 96% and was related to the presence of YST. Central patholo gic review revealed aspects of morphologic diagnosis that were most fr equently misinterpreted by contributing pathologists. These included t he classification of differentiating tissues as immature and the failu re to recognize two well-differentiated patterns of YST (the hepatoid pattern resembling fetal liver and the well-differentiated glandular p attern resembling fetal lung or intestine). Such foci were often overl ooked. The authors conclude that the presence of microscopic loci of Y ST, rather than the grade of IT, per se, is the only valid predictor o f recurrence in pediatric IT at any site.