We describe a distinctive benign tumor of the kidney in a 48-year-old woman, which was composed of well differentiated ducts set in the spindle cell stroma which was muscle actin, smooth muscle actin and desmin positive, and was morphologically similar to the ovarian stroma. No immature appearing epithelial renal or mesenchymal tissue was present in the tumor. Histologically, the tumor differed from the nephrogenic adenofibroma and the rare cases of adult Wilms tumors, mesoblastic nephromas and cystic nephromas.
"Mixed epithelial and stromal tumor of the kidney (MESTK), is a rare kidney tumor . The tumor was first identified by Michal and Syrucek in 1998  and has been ariously termed ‘cystic hamartoma of the renal pelvis,’ ‘adult mesoblastic nephroma,’ ‘cystic nephroma,’ ‘mature nephroblastic tumor’ or ‘cystic partially differentiated nephroblastoma.’ To date, approximately 100 cases have been reported , with most of these reports focusing on the pathological and radiological features of the tumors. "
[Show abstract][Hide abstract] ABSTRACT: Mixed epithelial and stromal tumor of the kidney (MESTK) is the term given to a class of uncommon biphasic tumors of the kidney, with few reported cases. We describe eight cases of MESTK with detailed clinicopathological data and follow-up information. With this report, we hope to increase clinical awareness that MESTK should be considered as one of the possible diagnoses for cystic renal mass, especially in peri-menopausal women or those who receive hormone therapy. In addition, regular follow-up is necessary for the any cases with malignant potential.
World Journal of Surgical Oncology 08/2013; 11(1):207. DOI:10.1186/1477-7819-11-207 · 1.41 Impact Factor
"Mixed epithelial and stromal tumor (MEST) is a rare, basically benign neoplasm of the kidney that has recently been recognized as a distinctive entity (1). It mostly occurs in middle-aged women and is associated with estrogen exposure (2). "
[Show abstract][Hide abstract] ABSTRACT: Mixed epithelial and stromal tumor (MEST) of the kidney is an unusual benign neoplasm that predominantly occurs in middle-aged females. It typically appears as a well-circumscribed multiseptate mass with solid components on computed tomography (CT) or magnetic resonance image (MRI), reflecting its characteristics of an admixture of stromal proliferation and epithelial cells consisting of multiple cysts. We present a rare case of 61-year-old woman with MEST, which manifested as a multilocular cystic mass with a polypoid component protruding into the renal pelvis and ureter. To our best knowledge, this is the first case of MEST extending into the ureter.
"The mixed epithelial and stromal tumour (MEST) of the kidney represents a recently described benign tumour, which has to be distinguished from other renal neoplasms . The term MEST was first introduced by Michal and Syucek in 1998. Morphologically, the tumour is characterized by a biphasic proliferation of stromal cells with an epithelial component showing cystic dilatation. "
[Show abstract][Hide abstract] ABSTRACT: Mixed epithelial and stromal tumour (MEST) represents a recently described benign composite neoplasm of the kidney, which predominantly affects perimenopausal females. Most tumours are benign, although rare malignant cases have been observed.
A 47-year-old postmenopausal female presented to the urologist with flank pain. A CT scan of the abdomen showed a 30-mm-in-diameter uniform mass adjacent to the pelvis of the left kidney. Surgical exploration showed a tumour arising from the lower anterior hilus of the left kidney. The tumour could be excised by preserving the kidney. By intraoperative frozen section the tumour showed characteristic features of MEST with epithelial-covered cysts embedded in an "ovarian-like" stroma. Additional immunohistochemistry investigations showed expression for hormone receptors by the stromal component of the tumour.
MEST typically presents in perimenopausal women as a primarily cystic mass. Commonly, the tumour arises from the renal parenchyma or pelvis. The tumour is composed of an admixture of cystic and sometimes more solid areas. The stromal cells typically demonstrate an ovarian-type stroma showing expression for the estrogen and progesterone receptors.
MEST represents a distinctive benign tumour entity of the kidney, which affects perimenopausal woman. The tumour should be distinguished from other cystic renal neoplasms. By imaging studies it is difficult to distinguish between a benign or malignant nature of the tumour. Thus, intraoperative frozen section is necessary for conservative surgery, since the overall prognosis is favourable and renal function can be preserved in most cases.
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