Classification of positive surgical margins and tumor recurrence after nephron-sparing surgery for small renal masses

Background: The association of positive margin and local recurrence after nephron-sparing. surgery (NSS) remains a notably controversial issue. The aim of the present study was to investigate the relationship between classification of positive surgical margins (PSMs) and tumor recurrence based pathological findings. Methods: Clinical, pathological, and follow-up data of 600 small renal cancer patients who underwent NSS between November 2007 and November 2017 at four hospitals in China were analyzed retrospectively. Results: Of the 600 reviewed patients, 20 had positive margins. During the follow-up period of 56 months, only three cases of tumor recurrence were identified. Pathological examination was performed, and subsequently a new classification criteria were proposed: 1) False PSMs, which could be further divided into three subtypes: i) no standard processing performed on pathological specimens (seven patients); incidental incision into the tumor during operation, with the tumor bed free of tumor residues (four patients); iii) part of the tumor pseudocapsule was noted to be remained in the tumor bed, with no signs of tumor residue (four patients). 2) True PSMs with two subtypes: i) a large number of residual tumor cells at the surgical margin (three patients); ii) incision of satellite tumor nodules detected around a large tumor (two patients). Conclusion: Taken together, PSMs in NSS were rarely found. Based on the pathological examination findings, PSMs can be divided into false positive and true positive. This being said, PSMs were determined to be poor predictors for local recurrence, with no predominant association with true tumor remnants in the majority of our evaluated cases. Through the key findings of our study, we concluded that PSMs should be carefully analyzed and treated on a case-by-case basis.