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European Urology
Volume 56, issue 1, pages 1-236, July 2009Letters to the Editor published online
Re: Rodolfo Montironi, Roberta Mazzuccelli, Antonio Lopez-Beltran, et al. Cystic Nephroma and Mixed Epithelial and Stromal Tumour of the Kidney: Opposite Ends of the Spectrum of the Same Entity? Eur Urol 2008;54:1237–46
Milan Hora a 
, Michal Michal b, Ondřej Hes b.
Accepted 9 January 2009, Published online 20 January 2009, page e3
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Refers to article:
Cystic Nephroma and Mixed Epithelial and Stromal Tumour of the Kidney: Opposite Ends of the Spectrum of the Same Entity?
Accepted 22 October 2007
December 2008 (Vol. 54, Issue 6, pages 1237 - 1246)
Article Outline
We have read with a great interest the review article by Montironi et al about cystic nephroma (CN) and mixed epithelial and stromal tumor of the kidney (MESTK) [1]. The review was prepared mainly from a pathologic point of view. We would like to add some clinical comments that are important for everyday clinical urologic praxis. At our institution, urologists are very familiar with these ideas because the concept of MESTK was described by our pathologists [2], and we have also published clinical opinions on these tumors [3], and [4]. We would like to make the following recommendations for everyday clinical praxis:
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1.1.
Differentiation of MESTK and CN is useless from a clinical point of view. The unifying term REST (renal epithelial and stromal tumor) [5], encompassing both MESTK and CN, is welcome for clinical praxis.
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2.2.
RESTs are classified with the Bosniak classification mainly as a type III and more rarely as types II and IV. Type IV indicates tumors with solid components.
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3.3.
Cystic lesions of Bosniak type I are indicated for follow-up (malignant tumor is nearly excluded), and type IV is indicated for radical treatment (there is a high risk of necrotic tumors with high malignant potential). Indications for Bosniak types II, IIF, and III are unclear. We recommend surgical treatment; priority is given to nephron-sparing surgery, if it is technically feasible, but in our opinion, most tumors are so advanced that resection is not possible. Why resection only? All tumors commonly found histologically in Bosniak II and III (RESTs and multilocular cystic renal cell carcinoma [MCRCC]) are “benign” [3]. We also have to consider Bosniak II multilocular cyst, but this is very rare and is also benign. The term carcinoma in MCRCC is a little misleading because no malignant course has been described for MCRCC [6]. Unfortunately, precise histologic criteria for MCRCC have not been defined to date.
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4.4.
It is impossible to preoperatively distinguish individual pathologic entities in Bosniak categories II and III by radiologic techniques (ultrasonography, computed tomography, magnetic resonance imaging). A preoperative biopsy of tumor provides no benefit.
The work was supported by Czech government research project MSM 0021620819.
Conflicts of interest: The authors have nothing to disclose.
References
- [1] R. Montironi, R. Mazzucchelli, A. Lopez-Beltran, et al.. Cystic nephroma and mixed epithelial and stromal tumour of the kidney: opposite ends of the spectrum of the same entity?. Eur Urol 54 (2008) (1237 - 1246) Abstract, Full-text, PDF, Crossref.
- [2] M. Michal, O. Hes, M. Bisceglia, et al.. Mixed epithelial and stromal tumors of the kidney. Virchows Archiv 445 (2004) (359 - 367) Crossref.
- [3] M. Hora, O. Hes, M. Michal, et al.. Extensively cystic renal neoplasms in adults (Bosniak classification II or III)—possible “common” histological diagnoses: multilocular cystic renal cell carcinoma, cystic nephroma, and mixed epithelial and stromal tumor of the kidney. Int Urol Nephrol 37 (2005) (743 - 750) Crossref.
- [4] M. Hora, J. Klečka, O. Hes, et al.. Mixed epithelial and stromal tumour of the kidney (MESTK). Eur Urol Suppl 4 (3) (2005) (12) Abstract, Full-text, PDF, Crossref.
- [5] J. Turbiner, M.B. Amin, P.A. Humphrey, et al.. Cystic nephroma and mixed epithelial and stromal tumor of kidney: a detailed clinicopathologic analysis of 34 cases and proposal for renal epithelial and stromal tumor (REST) as a unifying term. Am J Surg Pathol 31 (2007) (489 - 500) Crossref.
- [6] W.S. Webster, R.H. Thomson, J.C. Cheville, C.M. Lohse, M.L. Blute, B.C. Leibovich. Surgical resection provides excellent outcomes for patients with cystic clear cell renal cell carcinoma. Urology 70 (2007) (900 - 904) Crossref.
Footnotes
a Department of Urology, Charles University Hospital, Plzen, Czech Republic
b Department of Pathology, Charles University Hospital, Plzen, Czech Republic
Corresponding author. Department of Urology, University Hospital, E. Beneše 13, 305 99 Plzeň, Czech Republic. Tel./Fax: +420 377402171.
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