Peritumoral pseudocapsule status according to pathological characteristics from robot-assisted laparoscopic partial nephrectomy for localized renal cell carcinoma

Objective: To investigate peritumoral pseudocapsule status in patients with renal cell carcinoma who underwent robot-assisted laparoscopic partial nephrectomy, and to examine predictive factors associated with the absence of peritumoral pseudocapsule.

Methods: A total of 367 patients with clinical T1 renal cell carcinoma who underwent robot-assisted laparoscopic partial nephrectomy were divided into two groups according to peritumoral pseudocapsule status. The groups were compared in terms of patient and tumor characteristics. Multivariate logistic regression analysis was carried out to identify predictive factors for the absence of peritumoral pseudocapsule.

Results: Of the 367 tumors, 323 (88%) were surrounded by a peritumoral pseudocapsule. The mean tumor size was 30 mm, and 70% of the patients were male. Tumors with a peritumoral pseudocapsule had a larger diameter than those without (31 vs 26 mm; P = 0.0008). A peritumoral pseudocapsule was observed in 92% of the clear cell, in 89% of the papillary and in 86% of the clear cell papillary renal cell carcinoma cases compared with just 50% in the chromophobe renal cell carcinoma cases (P < 0.0001). Sex, age, Fuhrman grade and tumor complexity did not differ among patients. A multivariate analysis showed that smaller tumor size (≥34 vs <34 mm, odds ratio 3.31; P = 0.0023) and chromophobe renal cell carcinoma (vs other subtypes, odds ratio 12.5; P < 0.0001) predicted an absence of peritumoral pseudocapsule.

Conclusions: Small tumor size and chromophobe renal cell carcinoma were significant predictors of a lack of peritumoral pseudocapsule, suggesting that a positive surgical margin must be avoided for these tumors when an enucleation technique is used for robot-assisted laparoscopic partial nephrectomy.