Tumor enucleation specimens of small renal tumors more frequently have a positive surgical margin than partial nephrectomy specimens, but this is not associated with local tumor recurrence.

Approaches to nephron-sparing surgeries (NSS) of renal lesions include partial nephrectomy (PN) and tumor enucleation (TE). Our objective was to examine the pathology of the pseudocapsule and status of the surgical margin in small renal masses treated by NSS and to correlate these findings with the surgical and oncological outcomes. All consecutive renal TE and PN specimens obtained during the period between January 2012 and December 2014, of which clinical follow-up was available, were included in this study. Pathologic features and clinical data were reviewed and analyzed. A total of 117 NSS specimens (59 EN, 58 PN) were reviewed. Clear cell renal cell carcinomas and paraganglioma had the thickest pseudocapsules (0.36 mm), while angiomyolipomas did not form a well-defined pseudocapsule. Other tumors were intermediate in their characteristics. The positive margin rate for TE and PN was 17.2 and 0 %, respectively. Compared to PN, TE involved a significantly shorter procedure time, less blood loss, and fewer post-operative complications. None of the patients from either group was found to have a local recurrence after follow-up imaging. Although positive surgical margins were more frequently seen in TE specimens, local tumor recurrence was comparable to PN. Thus, TE is a reasonable choice for pT1 renal tumors, especially for those without a prominent infiltrative growth pattern.