A prospective, multicenter analysis of pseudocapsule characteristics: Do all stages of renal cell carcinoma have complete pseudocapsules?

Objectives To assess the characteristics of pseudocapsule (PC) in localized renal cell carcinoma (RCC) by analyzing the rates of completeness of PC and pseudocapsular invasion and clinical and pathological risk factors of it. Materials and methods Between February 2013 and September 2015, data were gathered prospectively from 180 consecutive patients who underwent partial nephrectomy or radical nephrectomy at 3 institutions, and 161 were enrolled. Evaluated factors included age and sex; histologic factors such as tumor diameter, stage, tumor subtype, necrosis, and Fuhrman grade; and clinical factors such as RENAL score; and completeness of PC. Results Only 94 tumors (58.4%) were surrounded by a continuous PC completely, 62 (38.5%) were partially surrounded, and 5 (3.1%) had no PC. Overall, 56 PCs (34.8%) were free from invasion, 58 PCs (36.0%) had partial invasion of PC without parenchymal invasion, and 47 PCs (29.2%) had parenchymal invasion. Defining parenchymal invasion as true pseudocapsular invasion, histologic diameter, RCC subtype, and completeness of PC were significant predictors for parenchymal invasion on multivariate analysis (P = 0.006, 0.046, and 0.002, respectively). Conclusions Rate of complete PC in RCC is relatively low in this study. The risk factors for pseudocapsular invasion were a histologic diameter greater than 4 cm, non–clear cell histology, and an incomplete PC. Surgeons must prepare for the possibility of a positive surgical margin if a tumor has at least one of these risk factors.