The natural history of small renal masses

Purpose: Ultrasound, computerized tomography and magnetic resonance imaging are widely available, Incidentally discovered small renal masses are repor ted more frequently. Most of these masses are low stage renal cell carcinom as. To understand better the natural history of these lesions and offer app ropriate management, we followed prospectively a series of patients with th is type of lesion. Materials and Methods: A total of 13 patients with radiologically detected solitary small renal masses who were unfit for or refused surgery were foll owed with abdominal imaging for a median of 42 months. Median patient age w as 69 years and mean lesion volume at diagnosis was 13.6 cm.(3) or 2.95 cm. in diameter. Growth rate was calculated based on tumor volume rather than bi-dimensional diameter. Individual slopes of tumor size in time were calcu lated. Results: Of the 13 patients 5 underwent surgery following a period of surve illance because of apparent tumor enlargement or new onset of symptoms. Pat hological evaluation revealed renal cell carcinoma in all 5. No patient had metastases. Only 2 tumors were fast growing and these were the only 2 case s in which symptoms developed. When these patients were excluded from analy sis average growth rate was 1.32 cm.(3) per year (p = 0.5, 95% confidence i nterval -3.00 to 5.76 cm.(3) per year), which was not statistically signifi cantly different from 0 slope or no growth. Conclusions: These results demonstrate that the growth rate of small renal tumors is variable, tumors that are destined to grow and possibly metastasi ze do so early and most small tumors grow at a low rate or not at all.