External histopathological validation of the surface-intermediate-base margin score.

PURPOSE: The surface, intermediate, and basis (SIB) is a system based on surgeon׳s visual assessment of the thickness of healthy parenchyma remaining on the intrarenal portion of the tumor. This system has been proposed to standardize the nomenclature of the resection technique (RT) during partial nephrectomy (PN). Our study aims at evaluating whether the SIB score visually assigned is related to the thickness of parenchyma measured by microscopy.

MATERIALS AND METHODS: Data of 52 patients submitted to PN from April to October 2015 were perspectively collected. All the excisions were performed following a "nonanatomical" strategy according to our institutional intention to resect the tumor with a visible margin of parenchyma. After the removal of the specimen, 2 trained examiners applied the SIB system: the intrarenal portion of the nodule was ideally divided into 3 circumferential sectors (surface, intermediate, and basis); on each of these was identified the area covered by the lowest amount of parenchyma (score specific area [SSA]); and a score descriptive of the thickness of parenchyma was assigned to each area. The RT performed (enucleation, enucleoresection, or wedge resection) was defined by the sum of the scores. The same examiners inked every SSAs with a different color and then dedicated pathologists, blinded of the scores assigned, and microscopically measured the parenchyma covering each SSA. The relationship between these values and the SIB scores was assessed.

RESULTS: According to the SIB nomenclature, the technique performed was enucleation for 31 patients (60%), enucleoresection for 16 (31%), and wedge resection for 5 (9%). For the surface SSA, the median/mean values of the thickness for S = 0 vs. S = 1 was 0.35/0.84 vs. 2.00/2.26mm and for the intermediate or base SSA, the median/mean value of the thickness for S = 0 vs. 1 vs. 2 was 0.35/0.47 vs. 1.00/1.50 vs. 2.00.5/2.33mm. All the comparison reached statistical significance.

CONCLUSIONS: The visual description of the surgical plane followed during PN according to the SIB system is related to the microscopic thickness of healthy parenchyma covering the tumor. The SIB system can correctly discriminate among different R techniques, and therefore could be a crucial tool to standardize the nomenclature of PN.