ORLANDO, FL USA (UroToday.com) - The oncological propriety of enucleative or ‘minimal-margin’ partial nephrectomy (PN) close to the tumor edge remains debatable. The research group analyzed histo-pathologic data to objectively characterize the tumor-parenchyma interface as regards the tumor pseudo-capsule (PC), adjacent parenchyma, and intra-renal arteries.
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The study included a total of 124 partial or radical nephrectomy specimen slides. Best representative sections were selected. Intra-/extra-renal tumor surface was evaluated to document PC presence/absence, thickness and invasion. Under a 4X objective, 4 mm2 sectors were parceled out at 1, 2, 3, 4 and 5 mm distance from the tumor to evaluate: peri-tumoral inflammation, glomerulosclerosis (GS), arteriosclerosis (AS), nephrosclerosis (NS), and number/diameter of peri-tumor arterioles.
The median tumor size was 3.5 cm (0.7-18.5). One hundred seven tumors (90%) were malignant. Of the tumors, PC was present in 119 (96%). Median PC thickness was 0.6 mm (0.1-2.6). Intra-renal PC was identified in 82% of malignant and 31% of benign tumors (p < 0.0001). Presence of intra-renal PC correlated with clear cell RCC histology (p=0.0001). PC invasion was noted in 53 tumors, 51 (96%) of which were malignant (p < 0.04). No patient with PC invasion showed a positive surgical margin. Severity of parenchymal changes decreased with increasing distance from tumor margin: at 1 mm distance, moderate-to-severe inflammation, GS, AS and NS occurred in 38%, 20%, 17%, and 32% of patients, respectively; conversely, at 5 mm distance, mild inflammation, GS, AS and NS occurred in 2.5%, 0.8%, 4% and 0.8%, respectively (p < 0.0001). Mean arteriolar diameter decreased closer to the tumor: 0.7 mm diameter at 5 mm distance from the tumor, compared to 0.3 mm diameter at 1 mm distance (p < 0.0001).
The authors conclude that most renal cancers have a well-developed PC. Invasion of intra-renal PC occurs in up to a third of cancers. No patient with PC invasion had a positive surgical margin. The tumor-parenchyma interface is histologically altered, with increasing parenchymal changes (inflammation, GS, AS, NS) and decreasing arterial diameter closest to the tumor. In conclusion for PN surgery, the plane of dissection immediately adjacent to the tumor appears to be histologically safe, with the least chance of hemorrhage.
Presented by Raed A. Azhar, MD at the American Urological Association (AUA) Annual Meeting - May 16 - 21, 2014 - Orlando, Florida USA
Los Angeles, CA USA
Written by Achim Lusch, MD, University of California (Irvine), and medical writer for UroToday.com