USC Institute of Urology ‘Minimal-margin’ Unclamped Partial Nephrectomy: Histologic & Anatomic Basis Raed Azhar, MD MS FRCSC Clinical Fellow, Robotic Surgery & Advanced Laparoscopy USC Institute of Urology

Tumor – Kidney Parenchyma Interface: Histologic Analysis

USC Institute of Urology Patients and Methods: n=124 H/E slides from 124 Nx/PNx specimens Presence of Pseudo-capsule (PC) Pseudo-capsule thickness Pseudo-capsule invasion by tumor

USC Institute of Urology Patients and Methods: Tumor – parenchyma 4 mm 2 sectors apportioned at 1, 2, 3, 4 and 5 mm from tumor edge Number and diameter of arterioles

USC Institute of Urology 4 mm 2 sectors apportioned at 1, 2, 3, 4 and 5mm from tumor edge Grade 0-1 = Mild; Grade 2-3 = Severe Inflammation Nephrosclerosis Arteriosclerosis Glomerulosclerosis

USC Institute of Urology Results: Median tumor size: 3.5 cm Malignant: 90% 96% of tumors had pseudo- capsule Median PC thickness: 0.6 mm Presence of intra-renal PC Cancers: 82% Benign: 31% (p<0.001) PC invasion: Cancers: 45% Benign: 15% (p<0.04) pT1a cancers had intra-renal PC invasion: 25%

USC Institute of Urology The closer to the tumor….the smaller the arterioles

USC Institute of Urology The closer to the tumor….the greater the inflammation, GS, NS, AS

USC Institute of Urology Conclusions: Most RCCs (82%) have a well-developed intra- renal pseudo-capsule. “Minimal- margin” PN appears histologically safe… and may result in less blood loss. Care is necessary to avoid positive margins

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