Congenital mesoblastic nephroma (CMN) is an uncommon tumour in the neo
natal period. Many CMNs are of ''typical'' histology and require no th
erapy other than nephrectomy. However, some are of ''atypical'' histol
ogy and are known to recur and metastasize. The use of chemotherapy in
the atypical variant and in case of recurrence has been a matter of c
ontroversy. The presence of tumour at the excision margin seems to be
the only important predictor of recurrence. The role of heminephrectom
y for localised lesions has not been defined. Five cases of CMN seen a
t the Royal Children's Hospital, Melbourne, are discussed. Two of them
were atypical histologically. One child had a heminephrectomy and is
among the first to have had this procedure for CMN. Current treatment
options are reviewed in relation to existing knowledge of the patholog
y and natural history of CMN.