Bilateral Wilms' tumor with anaplasia: lessons from the National Wilms' Tumor Study

The purpose of this study was to evaluate whether initial diagnostic technique influenced the ability to identify anaplastic histology, to determine the time interval to diagnosis of anaplasia, and to delineate the incidence of discordant pathology in bilateral Wilms' tumor. We hypothesized that delay in diagnosis of anaplasia could affect time to appropriate surgery and intensive multimodality therapy.

One hundred eight-nine children were enrolled in the fourth National Wilms' Tumor Study with synchronous bilateral tumors, 27 of whom were eventually shown to have anaplastic histology. Initial diagnostic technique, time interval to diagnosis of anaplasia, and the incidence of discordant pathology were determined.

Anaplasia was identified in 0 of 7 tumors by core needle biopsy, 3 of 9 tumors by open wedge biopsy, and in 7 of 9 cases by partial or complete nephrectomy. The mean duration of first chemotherapy regimen (DD or EE) was 20, 39, and 36 weeks, respectively, before anaplasia was identified at second surgery. Discordant pathology between bilateral tumors was identified on final tissue diagnosis in 20 patients. Only 4 patients had anaplastic tumors in both kidneys.

Core needle biopsy did not identify anaplasia in 7 of 7 children. Open biopsy or partial/complete nephrectomy identified anaplasia at initial diagnostic procedure in 10 of 18 children. Twenty of 24 patients at final tissue diagnosis had discordant pathology between the 2 kidneys. Earlier interval incisional biopsy or resection may identify anaplastic histology and limit the duration of chemotherapy targeted to favorable histology for children with bilateral Wilms' tumor and anaplasia.