Wilms' tumor: evaluation of histological features.

In order to evaluate the factors relating to prognosis, a clinico-pathological study was made in 27 patients with Wilms' tumor. Among these 27 cases, 10 survived more than two years after nephrectomy, 16 died within four days up to two years, and one patient could not be followed up. The younger age group and earlier stage of the disease showed more favorable prognosis. The tumor size, location, and number of tumor nodules had no effect on prognosis. Both the lymphatic and capsular invasions were common in the fatal cases. No vascular invasion was seen in any patient that had preoperative radiotherapy. Among the 10 survivors, six patients had received preoperative irradiation, whose tumors revealed a mesoblastic pattern. Polycystic structures were found in two surviving cases. One survivor's tumor contained prominent squamous epithelium. Another case showed predominance of undifferentiated spindle cells. The undifferentiated mesenchymal type with sarcomatous pattern would not always represent unfavorable prognosis. The tumor with mesoblastic pattern after radiotherapy and those with polycystic structure showed low-grade malignancy and maturation of stromal cells and tubules, respectively.