Purpose: To determine the rational surgical margin for pathological T1b renal cell carcinoma (RCC). Materials and Methods: This retrospective study included surveys of 60 patients with T1bN0M0 RCC who underwent radical nephrectomy (RN, n = 40) or partial nephrectomy (PN, n = 20) between October 2008 and Decem-ber 2014 at the Sun Yat-sen Memorial Hospital affiliated with Zhongshan University. Specimens were collected from 6 sites at the tumour periphery for RN and PN, and at suspected sites on

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... e tumour surface for PN in addition. The histological subtype, pathological grade, surgical margin, pseudocapsule completeness, distribution of satellite foci, and largest distance between the extra-pseudocapsule lesion and primary tumour (DEP) were evaluated. This paper will analyse the relationships between these factors. Results: The positive surgical margin rate was 10% in patients undergoing PN. The study found no significant relationships between the incidence of satellite foci and tumour diameter, Fuhrman grade, or histological subtype (all P > 0.05). However, male sex, positive surgical margins, and an incomplete pseudocapsule were associated with the incidence of satellite foci (P < 0.05). Cases with satellite foci tended to show positive surgical margins. The DEP was <1.0 mm for all tumours, but there were no significant relationships between the DEP and the tumour diameter, pathological grade, or histological subtype (P > 0.05). Conclusion: In T1b RCC, a 1-mm surgical margin would be sufficient to attain integrated resection of the primary tumour and its cancerous tissue beyond the pseudocapsule. PN was insufficient to prevent a positive surgical margin , most likely due to the presence of satellite foci.