[Non-radiological investigation of cystic renal tumours].

Cystic renal tumours represent 5% of all renal tumours. 1% of them are malignant. Non-radiological investigation of cystic renal tumours is still a controversial issue, essentially due to the rarity of these tumours. Although Bosniak class I and IV tumours theoretically do not present any diagnostic difficulties, it is difficult to confirm or exclude the malignancy of class II and III tumours at the time of their discovery. Percutaneous histological or cytological samples give a high rate of false-negative results and are difficult to interpret, but repeated specimens may avoid surgical exploration in one half of cases. Some authors adopt a more invasive approach due to the low yield of these examinations and the life-threatening risk related to the tumour. The difficulty of frozen section examination is due to the fact that it must specify the nature of the lesion and not the surgical margin with a considerable risk of false-negative results, especially when the tumour is confined to the cyst or when it is necrotic. One possible line of research could be analysis of the composition of cyst fluid, but a more readily available solution would consist of adaptation of Bosniak's classification in order to improve its inter-observer reproducibility and therefore reduce the need for invasive examinations.