[Cystic renal tumours in children]

To present clinico-pathological features of cystic renal tumours of childhood and to discuss criteria for their diagnosis and classification.

Renal tumours of childhood diagnosed at the Department of Pathology, Mother and Child Health Institute, New Belgrade, in the 1976-1990 period. In the analysys and classification of these tumours criteria of the International Society for Paediatric Oncology and the National Wilms' Tumor Study were used.

There were 133 renal tumours diagnosed, and five of them were cystic. Further histological examination revealed that 3 of them were cystic partially differentiated nephroblastomas (CPDN), one cystic nephroma (CN), and one Wilms' tumour (WT) with cystic areas. All children were treated according to the SIOP protocol and showed no evidence of the tumour at follow-up (at least 6 years).

Cystic renal tumours of childhood represent the spectrum of lesions that include CN, CPDN and WT with multicystic areas. CN is a bening multilocular tumour composed of non-communicating cysts separated by septa containing mature elements only. CPDN is a low risk malignant tumour characterised by the presence of the poorly differentiated elements (blastema) within the septa. WT with multicystic areas contains both cystic and solid areas composed of the same elements as classical WT. CN and CPDN follow a favourable course and they are treated with surgery only while WT with multicystic areas requires the same therapy as the classical WT including surgery, hemio- and radiotherapy. Since other renal tumours in children, such as clear cell sarcoma of kidney and mesoblastic nephroma, can be cystic too, the precise diagnosis of the cystic renal lesions is mandatory for their appropriate treatment.