To analyze the pathological characteristics and explore the optimal surgical margins (SM) of nephron-sparing surgery (NSS) for stage T renal carcinoma (4-7 cm) on preoperative imaging.
The clinical and pathological data of 245 cases of stage T kidney cancer from September 2013 to December 2017 were collected and reviewed retrospectively. The radical nephrectomy (RN) was performed on 174 cases and other 71 cases accepted NSS. There were 158 males and 87 females, with a mean age of 59.6 years and mean tumor size of 5.3 cm.
Through postoperative pathological examination, 209 (85.3%) cases were confirmed renal clear cell carcinoma and 219 (89.4%) cases were surrounded with visible peritumoralpseudocapsule (PC). 26 (10.6%) cases of cancerous cells invaded beyond peritumoral PC and into renal parenchyma. The infiltrative depth into renal parenchyma beyond PC was all limited in 3 mm and the cases of ≤1, 1-2 and 2-3 mm were 7 (26.9%), 16 (61.5%) and 3 (11.5%), respectively. Multifocal tumors were discovered in 24 (9.8%) cases. The average resection margin for partial nephrectomy was 5 mm (3-7 mm).
For stage T renal tumors, NSS is acceptable and a 3 mm of surgical margin is safe and suitable to avoid positive SM.

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