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

https://doi.org/10.1016/j.urolonc.2017.01.003Get rights and content

Abstract

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.

Introduction

The purpose of partial nephrectomy (PN) is to perform complete tumor removal with negative surgical margins (SMs) while preserving the maximum amount of healthy, vascularized renal tissue. Historically, the standard technique of PN involved excising a 1-cm margin of renal parenchyma to achieve a reliable negative margin and minimize the risk of local recurrence. This arbitrary 1-cm SM was introduced in 1950 by Vermooten [1]. However, a recent series report indicated that tumor margin width during PN is not associated with the likelihood of local recurrence. If a negative margin is achieved, even a 1-mm margin width is adequate and oncologically equivalent to a 1-cm margin width [2], [3], [4], [5].

Tumor enucleation (TE) consists of bluntly dissecting the pseudocapsule (PC) of the renal tumor along a natural plane from the surrounding tissue without removing a rim of renal parenchyma [6]. In contrast, conventional PN consists of sharply cutting a thin rim of renal parenchyma along with the tumor. Several studies have shown that TE not only is oncologically safe with maximal preservation of renal parenchyma but also appears to provide technical benefits, including reduced entry into the renal sinus, less need for tumor bed suturing, and shorter operative time in cases of T1a renal cell carcinoma (RCC) [6], [7], [8], [9]. However, the oncologic safety of TE remains controversial, as the technique could potentially result in a higher rate of local recurrence by inducing a positive SM [10].

With the evidence of comparable oncologic outcomes of PN and the risk of de novo renal failure after radical nephrectomy (RN) for a small renal tumor, the attention is now focused on expanding and setting the indications of PN in larger tumors. Recent reports have shown that PN achieves local tumor control equivalent to RN for RCC with a diameter of 4 to 7 cm [11], [12], and the recent European Association of Urology guidelines expanded its indication to include solitary RCC up to a diameter of 7 cm, whenever technically feasible [13]. Given that tumors with larger diameters are located deeper in the renal parenchyma, certain surgeons tend to use TE rather than PN, intentionally or unintentionally, owing to concerns related to functional outcome and the risk of damage to renal vessels and collecting systems during PN for larger RCC.

The aim of this study was to assess the characteristics of PC in T1a and larger RCC by analyzing the rates of completeness of PC and pseudocapsular invasion and clinical and pathological risk factors for pseudocapsular invasion in RCC.

Section snippets

Study population

This research was designed as a prospective multicenter study. After obtaining approval from the institutional review board of each institution, data were gathered prospectively between February 2013 and September 2015 from 180 consecutive patents with RCC who underwent PN or RN at 3 institutions in Korea. Overall, 15 patients with a pathologically proven benign tumor, 3 patients with a positive SM after PN, and 1 patient who refused to participate in the study were excluded.

Pathologic assessment

Before this

Results

Table 1 shows patient, tumor, and PC characteristics. The median age of patients was 58 years (interquartile range: 49–67.5 y), and 117 (72.7%) were male. The median histologic tumor diameter was 3.00 cm (interquartile range: 2.00–4.95 cm). A cancer stage of T1a was confirmed in 108 patients, T1b in 32, T2 in 13, and T3a in 8. Seven cases were given a Fuhrman grade of G1, 92 were G2, 52 were G3, and 10 were G4. The histologic subtype was clear cell in 134 cases, papillary in 13, chromophobe in 6,

Discussion

Recent studies on peritumoral PCs and the risk factors for pseudocapsular invasion are summarized in Table 3 [17], [18], [19], [20], [21], [22], [23]. Compared with previous studies, this study had several unique characteristics. First, we assessed only intrarenal PCs. Second, we defined true pseudocapsular invasion as only parenchymal invasion. Third, we assessed completeness of PC and pseudocapsular invasion as different categories. Fourth, because of the prospective study design, we were

Conclusions

Rate of complete PC in RCC is relatively low in this study. Therefore, the PN, especially TE technique, should be performed with extreme care, if at all. The risk factors for parenchymal invasion were a large histologic diameter of more than 4 cm, non–clear cell histology, and incomplete PC. If the tumor is suspected to have at least one of these risk factors preoperatively, the surgeon must prepare for the possibility of a positive SM.

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This work was supported by the 2013 Korean Urological Oncology Society Research Grant. This study was supported by a research Grant from Korea University Medical College (Seoul, Korea).

1

Seok Cho and Jeong Hyeon Lee are co-first authors who have both contributed equally to this work.

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