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.

LM cysts lined by simple epithelium with hobnailing, stroma has an ovarian look (basophilic, spindle cells)
LM DDx cystic nephroma, 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.

Turbiner et al.[1] have suggested that cystic nephroma and mixed epithelial and stromal tumour (MEST) are one tumour; the proposed lumping term renal epithelial and stromal tumour, abbreviated REST.


  • Rare - approximately 1.5% of renal neoplasms.[2]
  • 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.[3]





  • ER +ve.
  • PR +ve.
  • CD10 +ve.


  • PAX8 +ve (8 of 8 tumours[4]).
  • AMACR +ve stromal & epithelial cells - based on a case report.[5]
  • Inhibin -ve/+ve (42% +ve in 14 cases[1]).
  • Calretinin +ve (69% +ve in 14 cases[1]).

See also


  1. 1.0 1.1 1.2 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.
  2. 2.0 2.1 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.
  3. 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.
  4. 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.
  5. 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.