Mixed epithelial and stromal tumors of the kidney. A report of 22 cases

Abstract

Mixed epithelial and stromal tumor of the kidney (MESTK) is a recently described subset of renal neoplasm that tends to occur in middle-aged and older women and is characterized by a distinctive histological appearance. To further characterize this lesion, we report the clinicopathological and immunohistochemical features of 22 additional cases from our institutional files. Grossly, the tumors ranged in size from 1 cm to 14 cm (mean 6.7 cm), were well circumscribed but unencapsulated, and showed a cystic cut surface. The tumors were composed of a spindle cell proliferation that resembled ovarian stroma, as well as an epithelial component lining the cystic structures, which usually consisted of flat to hobnailed cells typical of collecting-duct epithelium. Areas displaying features of Mullerian differentiation were also documented in 6 cases, including epithelium of endometrioid, tubal, clear cell and squamous cell type as well as one case showing an architecture that closely resembled Mullerian adenofibroma and adenosarcoma. Follow-up in 14 patients (average 4.4 years) showed no evidence of recurrence or metastasis. We believe these tumors represent the renal counterpart of similar mixed epithelial and stromal neoplasms occurring in the biliary tract and pancreas, which is also characterized by cystic structures lined by epithelium, admixed with ovarian-type stroma. The differential diagnosis for these tumors includes cystic nephroma and cystic partially differentiated nephroblastoma, which we believe to represent clinically and morphologically distinct entities from MESTK. In particular, the distinction from cystic nephroma in adult male patients is emphasized, and two cases of this entity are included in the study for comparison.

Mixed epithelial and stromal tumour of the kidney: imaging features

“…Mixed epithelial and stromal tumours (MEST) are rare neoplasms of the kidney that have a characteristic histological appearance [1,2]. Their typical composition is an admixture of spindle cells that resemble ovarian stroma and an epithelial component that lines a variable cystic architecture [1,2].…”

“…Their typical composition is an admixture of spindle cells that resemble ovarian stroma and an epithelial component that lines a variable cystic architecture [1,2]. Before 1998, multiple renal tumours with the same histology were assigned a variety of diagnoses [1].…”

“…Their typical composition is an admixture of spindle cells that resemble ovarian stroma and an epithelial component that lines a variable cystic architecture [1,2]. Before 1998, multiple renal tumours with the same histology were assigned a variety of diagnoses [1]. A unifying term was not available until Michal and Syrucek [3] proposed the current name and reported a case with distinctive solid and cystic morphology [2,4].…”

“…A strong association with oestrogen exposure was proposed. Of the 90 patients reported who had MEST [1][2][3][5][6][7][8][9][10][11][12][13][14][15][16][17][18], almost all have been women [2,4]. Many of these patients were perimenopausal with a history of long-term oestrogen replacement at the time of diagnosis [2].…”

“…Although there are case reports and series in the pathology literature [1][2][3]6,7,[9][10][11][12][13][14]16,17] there are few published reports describing the imaging findings of MEST [5,8,19]. To the best of our knowledge, the largest radiological study described the imaging features in three patients [5].…”