OBJECTIVE: To investigate the incidence and associated factors of multicentricity in renal cell carcinoma (RCC) in Chinese patients. METHODS: One hundred and two kidney samples from radical nephrectomy due to RCC were step sectioned at 3 mm intervals and examined. All tissue abnormalities were removed, stained and examined for multicentricity. Then, on each slice of the sample, both the parenchymal margin of 15 mm beyond the pseudocapsule and tissue around the renal sinus were continuously sectioned and examined for completeness of the pseudocapsule and vascular and lymph node invasion. The relationship between muliticentricity and other pathological parameters was evaluated. RESULTS: The incidence of multicentricity was 15.7% (16/102); it was significantly lower in primary tumors 4.0 cm (4.9%, 2/41 vs 23.0%, 14/61; chi(2) = 6.055, P = 0.014). The incidence was 9.8% (8/82) in tumors without vascular invasion and 40.0% (8/20) in those with it (P = 0.003, Fisher's exact test). The incidence of multicentricity was 1.9% (1/53) in tumors with a complete pseudocapsule and 30.6% (15/49) in those without it (chi(2) = 15.885, P = 0.000). The grade, stage, subtypes and lymph node invasion of the primary tumor were not significantly associated with multicentricity. Multiple logistic regression analysis showed that pseudocapsular incompleteness and vascular invasion were two significant predictors of RCC multicentricity (P = 0.005 and 0.023). CONCLUSIONS: The incidence of multicentricity of RCC in this group of patients was in accordance with published studies. Multifocality was significantly associated with tumor size, pseudocapsule completeness and vascular invasion. NSS should be limited to tumors less than 4.0 cm when the contralateral kidney is normal and careful long-term follow-up is necessary in tumors with positive vascular invasion and incomplete pseudocapsule.
