Mixed epithelial and stromal tumour (MEST) of the kidney is an uncommon and recently recognised distinct neoplasm that should be distinguished from other renal neoplasms.
There is a female preponderance 10:1 1 with tumours occurring predominantly in middle-aged peri-menopausal women and older women. There is a possible link with oestrogen therapy and other hormonal treatment, including GnRH agonists 2,5.
Most are incidental findings. Can also present as palpable abdominal or flank mass, flank pain, and/or haematuria.
This benign kidney tumour shows solid and cystic architecture and is composed of epithelial and mesenchymal elements 4-5:
- the epithelial component is composed of dilated tubules and cysts lined by a simple layer of cuboidal to columnar epithelium, often with prominent surface 'hobnail' outline
- the epithelium stains strongly for renal lineage markers (PAX8) and for CK7
- the surrounding stromal component is fibrous to spindled to focally muscular and shows expression of ER and PR; it is often described as 'ovarian-type stroma'
The lesion is usually well circumscribed from the surrounding renal parenchyma and perinephric fat and lacks features of malignancy including invasive growth, necrosis or significant cellular atypia.
It is typically seen as a multiloculated cystic renal mass with a variable proportion of solid and cystic components and containing internal septa. The latter may demonstrate heterogeneous and delayed contrast material enhancement 3.
Treatment and prognosis
They are almost universally benign, however, rare cases with malignant transformation, recurrence, and metastasis have been reported 1,6.
- multicystic renal cell carcinoma: indistinguishable on imaging 7
- 1. Mohanty SK, Parwani AV. Mixed epithelial and stromal tumors of the kidney: an overview. Arch. Pathol. Lab. Med. 2009;133 (9): 1483-6. Pubmed citation
- 2. Adsay NV, Eble JN, Srigley JR et-al. Mixed epithelial and stromal tumor of the kidney. Am. J. Surg. Pathol. 2000;24 (7): 958-70. Pubmed citation
- 3. Chu LC, Hruban RH, Horton KM et-al. Mixed epithelial and stromal tumor of the kidney: radiologic-pathologic correlation. Radiographics. 2010;30 (6): 1541-51. doi:10.1148/rg.306105503 - Pubmed citation
- 4. Wang CJ, Lin YW, Xiang H et-al. Mixed epithelial and stromal tumor of the kidney: report of eight cases and literature review. World J Surg Oncol. 2013;11 (1): 207. doi:10.1186/1477-7819-11-207 - Free text at pubmed - Pubmed citation
- 5. Srigley JR, Delahunt B, Eble JN et-al. The International Society of Urological Pathology (ISUP) Vancouver Classification of Renal Neoplasia. Am. J. Surg. Pathol. 2013;37 (10): 1469-89. doi:10.1097/PAS.0b013e318299f2d1 - Pubmed citation
- 6.Jung SJ, Shen SS, Tran T et-al. Mixed epithelial and stromal tumor of kidney with malignant transformation: report of two cases and review of literature. Hum. Pathol. 2008;39 (3): 463-8. doi:10.1016/j.humpath.2007.08.008 - Pubmed citation
- 7. Brant WE, Helms C. Fundamentals of Diagnostic Radiology. Lippincott Williams & Wilkins. (2012) ISBN:1608319113. Read it at Google Books - Find it at Amazon