Small renal tumors: correlation of clinical and pathological features with tumor size

We analyzed the association between tumor diameter and pathological stage, histological subtype, tumor grade and the incidence of metastases in renal cell carcinoma with a diameter of up to 4 cm (clinical stage T1a).

We analyzed a consecutive series of 663 patients with renal tumors 4 cm or less who underwent surgery at our institution between 1990 and 2006. After excluding 115 patients (17.3%) with benign tumors 548 with renal cell carcinoma were included in the study. Tumor size on preoperative imaging was correlated with pathological stage, tumor grade, histological subtype and incidence of metastases at diagnosis. For data analysis tumors were stratified by tumor diameter into 3 groups, including 2 cm--99 patients with tumors up to 2 cm, 3 cm--234 with tumors between 2.1 and 3.0 cm, and 4 cm--215 with tumors between 3.1 and 4.0 cm in diameter.

Median clinical diameter of renal cell carcinoma in the whole series was 2.93 cm (range 0.8 to 4.0). Tumor stage was pT1a, pT1b and pT3 in 84.5%, 8.0% and 7.5% of cases, respectively. Tumor grade was 1 to 3 in 24.5%, 65.0% and 10.6% of cases, respectively. The renal cell carcinoma histological subtype was clear cell carcinoma in 77.9% of patients, papillary carcinoma in 15.3% and chromophobe carcinoma in 6.8%. Advanced tumor stage (pT3) was found in 3.0%, 5.1% and 12.1% of the patients in the 2, 3 and 4 cm groups, respectively (p <0.05). Grade 3 was found in 7.1%, 9.0% and 14.0% of the patients in the 2, 3 and 4 cm groups, respectively (p <0.05). Metastases at diagnosis were found in 3.0%, 2.6% and 6.0% of the patients in the 2, 3 and 4 cm groups, respectively.

Negative prognostic features increase with tumor diameter and they are associated with even small tumors. However, above a tumor size of 3.0 cm there is a sharp increase in the incidence of negative prognostic parameters. New diagnostic tests are warranted to better stratify patients with respect to treatment aggressiveness for small incidental renal tumors.