THE RELATIONSHIP BETWEEN MICROSUBSTAGING VARIABLES, AGE AT DIAGNOSIS, AND TUMOR WEIGHT OF CHILDREN WITH STAGE I/FAVORABLE HISTOLOGY WILMS-TUMOR - A REPORT FROM THE NATIONAL WILMS-TUMOR STUDY

Background. The purpose of this study was to determine the relationship between histologic microsubstaging variables, patient age, and tumor specimen weight in patients with Stage I/favorable histology Wilms' tumors. Methods. The authors reviewed all randomized patients from the Fourth National Wilms' Tumor Study, who had Stage I/favorable histology Wilms' tumors evaluated for one or more of the microsubstaging variables: (1) the presence of an inflammatory pseudocapsule, (2) renal sinus invasion, (3) tumor in the intrarenal vessels, and (4) tumor capsule invasion. The authors determined the correlation between microsubstaging variables and age at diagnosis or tumor specimen weight. Results. Patients who were younger than 2 years of age at diagnosis were significantly more likely to have all negative microsubstaging variables. Patients who had tumors weighing less than 550 g were more likely to have all negative microsubstaging variables. However, neither renal sinus invasion nor tumor in the intrarenal vessels was more frequent in tumors weighing more than 550 g. Conclusions. An age at diagnosis of younger than 2 years and a tumor specimen weight of less than 550 g are highly correlated with the absence of adverse microsubstaging variables. The clinical variables of age at diagnosis and tumor specimen weight, compared with the assessment of microsubstaging variables, have the practical advantage of being more objectively determined and not requiring a central pathologic review for confirmation.