MRI Characteristics and Clinical Value of the Tumor Pseudocapsule in the Local Staging of Renal Cell Carcinoma
Main Article Content
Abstract
ABSTRACT
Objective:
To describe the magnetic resonance imaging (MRI) characteristics of the tumor pseudocapsule and to evaluate the value of the MRI-Cap classification in predicting pseudocapsule invasion on histopathology (i-Cap) and local pathological stage in renal cell carcinoma (RCC).
Materials and Methods:
This retrospective descriptive study included 62 patients with RCC who underwent surgical treatment at Bach Mai Hospital between 2024 and 2026. All patients underwent preoperative MRI. The tumor pseudocapsule was assessed using the MRI-Cap classification system, including four categories: MRI-Cap 0 (absence of pseudocapsule), MRI-Cap 1 (continuous pseudocapsule), MRI-Cap 2 (focal pseudocapsule interruption), and MRI-Cap 3 (marked or extensive pseudocapsule discontinuity). Agreement between MRI-Cap and i-Cap classifications was evaluated using Cohen’s kappa coefficient. The associations between MRI-Cap and pathological T stage (pT), RENAL nephrometry score, and surgical approach were analyzed using appropriate statistical tests.
Results:
A tumor pseudocapsule was identified on MRI in 53 of 62 cases (85.5%). According to the MRI-Cap classification, MRI-Cap 1 was the most frequent category (46.8%), followed by MRI-Cap 2 (24.2%), MRI-Cap 0 (14.5%), and MRI-Cap 3 (14.5%).
The MRI-Cap classification showed good agreement with the histopathological i-Cap classification, with an overall concordance rate of 85.5% (53/62 cases) and a Cohen’s kappa coefficient of 0.758. Correct classification rates for i-Cap 0, i-Cap 1, i-Cap 2, and i-Cap 3 were 100.0%, 80.0%, 85.7%, and 100.0%, respectively. MRI-Cap 3 demonstrated the highest diagnostic performance for predicting i-Cap 3, with a sensitivity of 100.0%, specificity of 98.1%, and accuracy of 98.4%.
Furthermore, MRI-Cap was positively correlated with pathological T stage (Spearman’s rₛ = 0.649, p < 0.001). The distribution of pT stages differed significantly among MRI-Cap groups (Fisher–Freeman–Halton exact test, p < 0.001). Notably, 88.9% of MRI-Cap 3 tumors were classified as pT3a, whereas no pT3a cases were observed in the remaining MRI-Cap groups. Tumors classified as MRI-Cap 3 also tended to have higher RENAL nephrometry scores and were more frequently treated with radical nephrectomy.
Conclusion:
The tumor pseudocapsule is a common MRI finding in patients with RCC. The MRI-Cap classification shows good agreement with histopathological i-Cap classification and is closely associated with local pathological stage. MRI-Cap 3 may suggest local tumor invasion and pT3a disease, thereby supporting preoperative risk stratification and surgical planning.
Keywords
Keywords: renal cell carcinoma, tumor pseudocapsule, MRI-Cap, i-Cap, local staging, perinephric invasion, magnetic resonance imaging.
Article Details
References
Netherlands; 2026. ISBN 978-94-92671-32-5.
2. Bellin MF, Valente C, Bekdache O, Maxwell F, Balasa C, Savignac A, Meyrignac O. Update on renal cell carcinoma
diagnosis with novel imaging approaches. Cancers (Basel). 2024;16(10):1926. doi:10.3390/cancers16101926.
3. Roy C, El Ghali S, Buy X, et al. Significance of the pseudocapsule on MRI of renal neoplasms and its potential application
for local staging: a retrospective study. AJR Am J Roentgenol. 2005;184(1):113-120. doi:10.2214/AJR.184.1.01840113
4. Papalia R, Panebianco V, Mastroianni R, et al. Accuracy of magnetic resonance imaging to identify pseudocapsule
invasion in renal tumors. World J Urol. 2020;38(2):407-415. doi:10.1007/s00345-019-02755-1.
5. Snarskis C, Calaway AC, Wang L, et al. Standardized reporting of microscopic renal tumor margins: introduction
of the renal tumor capsule invasion scoring system. J Urol. 2017;197(1):23-30. doi:10.1016/j.juro.2016.07.086.
6. Toguchi M, Takagi T, Ogawa Y, et al. Detection of a peritumoral pseudocapsule in patients with renal cell carcinoma
undergoing robot-assisted partial nephrectomy using enhanced MDCT. Sci Rep. 2021;11(1):2245. doi:10.1038/
s41598-021-81922-0.
7. Iwamoto H, Nosaka K, Miyoshi H, et al. Is preoperative magnetic resonance imaging in a daily clinical setting useful
to evaluate tumor invasion beyond the pseudocapsule in renal cell carcinoma? Yonago Acta Med. 2021;64(4):345-
352. doi:10.33160/yam.2021.11.004.
8. Amin MB, Greene FL, Edge SB, et al. The Eighth Edition AJCC Cancer Staging Manual: continuing to build a bridge
from a population-based to a more personalized approach to cancer staging. CA Cancer J Clin. 2017;67(2):93-99.
doi:10.3322/caac.21388.
9. Minervini A, di Cristofano C, Lapini A, et al. Histopathologic analysis of peritumoral pseudocapsule and surgical
margin status after tumor enucleation for renal cell carcinoma. Eur Urol. 2009;55(6):1410-1418. doi:10.1016/j.
eururo.2008.07.038.
10. Ganeshan D, Khatri G, Ali N, et al. ACR Appropriateness Criteria® Staging of Renal Cell Carcinoma: 2022 Update.
J Am Coll Radiol. 2023;20(5S):S246-S264. doi:10.1016/j.jacr.2023.02.008.