[Watchful waiting and active surveillance of small renal masses].

The incidence of small renal masses ≤4 cm is increasing due to the widespread use of cross-sectional imaging. The majority of these represent indolent forms, but the risk for developing metastases is reported in up to 6% of patients. Particularly in old and comorbid patients surgery might be harmful overtreatment. Thus, there is an increasing demand to establish oncologically safe active surveillance protocols. Radiographic or biopsy-based biological markers to appropriately designate candidates for active surveillance are currently the focus of research.