Heterogeneity of Wilms' tumour blastema. An immunohistological study.

Antigen expression in fourteen cases of Wilms' tumour was assessed with a panel of monoclonal antibodies. The panel included antibodies reactive with intermediate filament proteins and antibodies reactive with membrane markers originally reported to be associated with small cell lung carcinoma. The immunohistological findings in the tumours were compared to results obtained in adult and fetal kidney. The antigen profile in the blastemal tissue component of the tumours revealed both characteristics of embryonic tissue and signs of early epithelial differentiation. In addition, the histologically apparent transition between blastema and tubules was shown to be reflected in a concurrently occurring and gradual increase in the number of expressed epithelial antigens. Between different tumours, heterogeneity in the degree of epithelial differentiation in the blastema was found. In addition, one case showing foci of anaplasia proved to have an entirely different antigen profile when compared with the other thirteen, non-anaplastic cases. This result is discussed in relation to the different clinical behaviour of focally anaplastic tumours. It is concluded that immunohistology can confirm and extend the histological classification of Wilms' tumour. In addition, new subtypes may be identified in this way.