There is a female preponderance 10:1 1 with tumors occurring predominantly in middle-aged peri-menopausal women and older women. There is a possible link with estrogen 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 hematuria.
This benign kidney tumor 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.
- multilocular cystic renal neoplasm of low malignant potential, formerly multilocular cystic renal cell carcinoma 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. Moch H, Cubilla AL, Humphrey PA, Reuter VE, Ulbright TM. The 2016 WHO Classification of Tumours of the Urinary System and Male Genital Organs-Part A: Renal, Penile, and Testicular Tumours. (2016) European urology. 70 (1): 93-105. doi:10.1016/j.eururo.2016.02.029 - Pubmed