Chemotherapy-induced histologic changes in Wilms' tumors.

The nephrectomy specimens of 21 patients with Wilms' tumor who received preoperative chemotherapy consisting of vincristine and actinomycin D, alone or in combination, were studied pathologically; 1 patient also received radiation therapy. Pathological material from 20 randomly selected patients with Wilms' tumor who did not receive preoperative chemotherapy was reviewed and used as a control. Twenty tumors were of favorable histology, and one was unfavorable; all control tumors were of favorable histology. The histological changes were diffuse. The most marked changes occurred in the undifferentiated stroma of 18 tumors: the stroma was edematous; had a fibrovascular background, granulation tissue, and histiocytes; and lacked atypical cells. The blastematous nodules were reduced in size and necrotic or undergoing necrosis in 5 cases. Differentiated elements, including glomeruloid, tubular, and rhabdomyoblastic components, were unaffected. Vascular changes, consisting of fibrinoid necrosis, thrombosis, and acute inflammation were prominent in 15 instances. Two tumors of favorable histology, including one that was a rhabdomyomatous Wilms' tumor, and the tumor of unfavorable histology were unchanged by the therapy. In contrast, the histological changes present in only 4 of the control group, while similar, were rather minimal and focal. This evaluation helps to define the susceptibility of the different elements in Wilms' tumor to chemotherapy.