New look at mesoblastic nephroma.

Thirty eight mesoblastic nephromas were studied. The age range of the patients was between the neonatal period and 18 months. The presence of cartilage is consistent with a mesoblastic origin, but squamous epithelium was a feature in three tumours. Particular attention was given to the adjacent renal tissue in which various histological features were noted: vacuolated and dysplastic tubules; cysts; and subcapsular epithelial tumourlets. The findings had aspects in common with both dysplastic kidneys and nephroblastoma. Classification of the tumours as normocellular and hypercellular was attempted, but there was considerable overlap. The behaviour of the tumour was good in all cases, although follow up was relatively short on some patients, and deaths from non-neoplastic causes occurred.