[Histopathology of nephroblastomas (author's transl)]

Nephrectomy specimens from 42 patients with nephroblastoma were investigated. With the exception of one specimen (the patient had been treated preoperatively), all of the tumors were suitable for grading procedures. When the tumors were classified by the grading procedure of Lawler et al. (1975), the moderately tubulus-rich type++ was the most common (22 out of 41 patients). When the classification of Beckwith and Palmer (1978) was applied, the mixed type of nephroblastoma dominated correspondingly (19 out of 41 patients). Patients with an increased risk can be identified particularly well with the classification of Beckwith and Palmer. The following histologic features are indications of an unfavourable prognosis: focal or diffuse "anaplasia" of the tumor tissue, or a sarcomatous component in a stroma-rich nephroblastoma. The children with sarcomatous nephroblastoma (5 patients) were remarkably young (the oldest was 16 months of age), whereas the children with anaplastic nephroblastoma (3 patients) were much older (62, 67, and 72 months). In five children equivalents of the nephroblastomatosis complex (nodular renal blastema in all 5 patients, sclerosing metanephric hamartoma in 2 patients, and Wilms' tumorlet in one patient) were found in the non-infiltrated tissue of the same kidney.