• renal neoplasm;
  • surveillance;
  • watchful waiting;
  • natural history;
  • tumor growth rate;
  • progression



The objective of the current study was to evaluate the outcome of a surveillance strategy in patients with renal masses.


The medical records of patients with renal masses diagnosed between January 1992 and May 2006 were reviewed retrospectively. In all, 45 patients with renal masses under observation were identified. Of these, 35 patients with 44 renal masses measuring <4 cm in dimension at the time of diagnosis and who were followed for at least 6 months were included in the review. Patients elected observation because of age, comorbidity, solitary kidney, or bilateral renal masses. Medical records were reviewed to determine tumor size and volume changes as well as clinical progression requiring treatment, the development of metastatic disease, or death.


A total of 35 patients (21 men and 14 women) with 44 renal masses were observed for a mean follow-up of 47.6 months. The mean age of these patients was 71.8 years. The majority of the patients (89%) were asymptomatic at the time of diagnosis. The mean and median initial tumor dimension was 2.2 cm and 2.2 cm, respectively (range, 0.5–4 cm). Of the 35 patients, 2 (5.7%) were lost to follow-up, 8 (22.9%) underwent surgical resection, and 9 (25.7%) died of other causes. The mean dimension growth rate was 0.21 cm/year (range, 0.03–1.9 cm/year). The mean and median volume growth rate was 2.7 cc/year and 1.4 cc/year, respectively. Progression to metastatic disease was identified in 2 patients (5.7%).


The majority of renal masses will grow if observed and some may require treatment. Initial tumor size cannot predict the natural history of renal masses. A small but non-negligible risk of developing metastatic disease exists in this patient population. Further research should focus on the role of biopsy and on identification of prognostic parameters allowing more accurate prediction of tumor growth and metastasis. Cancer 2007. © 2007 American Cancer Society.