Mixed epithelial and stromal tumour of the kidney

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Mixed epithelial and stromal tumour of the kidney
Diagnosis in short

Mixed epithelial stromal tumour of kidney. H&E stain.

Synonyms mixed epithelial and stromal tumour family (term recommended in WHO 2016 classification)

LM cysts lined by simple epithelium with hobnailing, stroma has an ovarian look (basophilic, spindle cells)
Subtypes on a spectrum with cystic nephroma, adult type
LM DDx cystic nephroma, pediatric type, tubulocystic renal cell carcinoma
IHC ER +ve, PR +ve, CD10 +ve
Gross renal mass, predominantly solid
Grossing notes total nephrectomy for tumour grossing, partial nephrectomy grossing
Site kidney - see kidney tumour

Prevalence rare
Prognosis benign

Mixed epithelial and stromal tumour of the kidney, abbreviated MEST, is a rare benign kidney tumour in the WHO classification of renal neoplasia.

In the 2016 World Health Organization classification of renal neoplasia, this tumour was lumped with cystic nephroma, adult type and the recommended term is mixed epithelial and stromal tumour family.[1]

Turbiner et al.[2] came-up with a cheeky term for the the tumour family (renal epithelial and stromal tumour, abbreviated REST) that didn't catch on.

This kidney tumour should not be confused with mixed epithelial-stromal tumour of seminal vesicle.[3]


  • Rare - approximately 1.5% of renal neoplasms.[4]
  • Benign.
  • Prevalence: males > females.


  • Solid and cystic mass - predominantly solid.



  • Cysts lined by simple epithelium with hobnailing - key feature.
  • Stroma has an ovarian look:
    • Blue (basophilic).
    • Spindle cells.


  • Parenchymal elements (e.g. glomueruli, tubules) are not found in the septa between the cysts.
  • May extend into the renal vein.[5]
  • The WHO 2016 classification considers it to be on a spectrum with cystic nephroma, adult type.[1]





  • ER +ve.
  • PR +ve.
  • CD10 +ve.


  • PAX8 +ve (8 of 8 tumours[7]).
  • AMACR +ve stromal & epithelial cells - based on a case report.[8]
  • Inhibin -ve/+ve (42% +ve in 14 cases[2]).
  • Calretinin +ve (69% +ve in 14 cases[2]).

See also


  1. 1.0 1.1 Moch, H.; Cubilla, AL.; Humphrey, PA.; Reuter, VE.; Ulbright, TM. (07 2016). "The 2016 WHO Classification of Tumours of the Urinary System and Male Genital Organs-Part A: Renal, Penile, and Testicular Tumours.". Eur Urol 70 (1): 93-105. doi:10.1016/j.eururo.2016.02.029. PMID 26935559.
  2. 2.0 2.1 2.2 Turbiner, J.; Amin, MB.; Humphrey, PA.; Srigley, JR.; De Leval, L.; Radhakrishnan, A.; Oliva, E. (Apr 2007). "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 (4): 489-500. doi:10.1097/PAS.0b013e31802bdd56. PMID 17414095.
  3. Reikie, BA.; Yilmaz, A.; Medlicott, S.; Trpkov, K. (Mar 2015). "Mixed epithelial-stromal tumor (MEST) of seminal vesicle: a proposal for unified nomenclature.". Adv Anat Pathol 22 (2): 113-20. doi:10.1097/PAP.0000000000000057. PMID 25664946.
  4. 4.0 4.1 Mai, KT.; Elkeilani, A.; Veinot, JP. (Apr 2007). "Mixed epithelial and stromal tumour (MEST) of the kidney: report of 14 cases with male and PEComatous variants and proposed histopathogenesis.". Pathology 39 (2): 235-40. doi:10.1080/00313020701230799. PMID 17454754.
  5. Xie, WL.; Lian, JY.; Li, B.; Tian, XY.; Li, Z. (Apr 2017). "Mixed epithelial and stromal tumor of kidney with renal vein extension: an unusual case report and review of literature.". Histol Histopathol 32 (4): 361-369. doi:10.14670/HH-11-800. PMID 27383188.
  6. Rogala J, Kojima F, Alaghehbandan R, Agaimy A, Martinek P, Ondic O, Ulamec M, Sperga M, Michalova K, Pivovarcikova K, Pitra T, Hora M, Ferak I, Marečková J, Michal M, Hes O (February 2020). "Papillary renal cell carcinoma with prominent spindle cell stroma - tumor mimicking mixed epithelial and stromal tumor of the kidney: Clinicopathologic, morphologic, immunohistochemical and molecular genetic analysis of 6 cases". Ann Diagn Pathol 44: 151441. doi:10.1016/j.anndiagpath.2019.151441. PMID 31862520.
  7. Karafin, M.; Parwani, AV.; Netto, GJ.; Illei, PB.; Epstein, JI.; Ladanyi, M.; Argani, P. (Sep 2011). "Diffuse expression of PAX2 and PAX8 in the cystic epithelium of mixed epithelial stromal tumor, angiomyolipoma with epithelial cysts, and primary renal synovial sarcoma: evidence supporting renal tubular differentiation.". Am J Surg Pathol 35 (9): 1264-73. doi:10.1097/PAS.0b013e31822539a1. PMID 21836481.
  8. Horsanali, MO.; Yilmaz, Y.; Ozer, K.; Kose, O.; Cakalagaoglu, F.; Etit, D. (Feb 2017). "Mixed Epithelial and Stromal Tumor of the Kidney: Two Case Reports of a Rare Benign Kidney Tumor.". Clin Genitourin Cancer 15 (1): e55-e59. doi:10.1016/j.clgc.2016.10.009. PMID 27865685.