Epithelial Stromal Tumor Research Articles

Quantifiable mRNA transcripts for tamoxifen-metabolising enzymes in human endometrium

Tamoxifen has been used in the management of receptor-positive breast cancer for >20 years. Usage confers an elevated risk of developing endometrial carcinoma. Its mechanism of carcinogenicity remains unresolved with controversy as to whether or not this is mediated through a genotoxic mechanism. Usage is not only associated with an elevated occurrence of endometrioid endometrial carcinoma, but also type 2 and mixed epithelial-stromal tumours (MESTs) that have a poorer prognosis. Following hysterectomy, endometrial tissues ( n = 18) classified as benign ( n = 6), non-tamoxifen-associated carcinoma ( n = 6) and tamoxifen-associated carcinoma ( n = 6) were obtained; quantitative gene expression was performed. Employing real-time RT-PCR, the relative gene expressions of phase I/II metabolic enzymes CYP1A2, CYP1B1 and CYP3A4, cathechol- O-methyltransferase ( COMT) and SULT2A1 were ascertained. Measurable mRNA transcripts, especially for those genes associated with tamoxifen bioactivation, were quantifiable in all the tissues examined. Whether this is evidence that generation of genotoxic tamoxifen metabolites may occur in human endometrial tissue remains to be ascertained.

ADENOCARCINOMA ENDOMETRIAL CONCOMITANTE CON TUMOR ESTROMAL BENIGNO DEL ENDOMETRIO

SUMMARY The association of epithelial and stromal malignant neoplasm is very rare, with few reported cases, rarer still is the prescence of malignant epithelial tumor and stromal benign tumor. We present the case of women aged 65 with preoperative diagnosis of endometrial carcinoma, which in the pathological examination was found an intramural benign endometrial stromal lesion, without continuity between both tumors.

Fat-Predominant Mixed Epithelial Stromal Tumor (MEST): Report of a Unique Case Mimicking Angiomyolipoma

A unique case of a mixed epithelial stromal tumor (MEST) that was predominantly composed of adipose tissue is reported here. Radiographically and grossly, the lesion was thought to be an angiomyolipoma, based upon its fatty appearance. Microscopically, the lesion was predominantly composed of mature adipose tissue but also contained clusters of bland tubules surrounded by smooth muscle bundles and collagen. By immunohistochemistry, the stroma labeled diffusely for estrogen and progesterone receptors, while the muscle bundles labeled for desmin. Melanocytic markers HMB45 and Melan A, typically positive in angiomyolipoma, were nonreactive. This case expands the morphologic spectrum of MEST to include mimics of angiomyolipoma.

Bilateral mixed epithelial stromal tumor in an end-stage renal disease patient: the first case report

Although first intimated in the 1970s, mixed epithelial stromal tumor has been recognized as a diagnostic entity for less than 10 years, with an identity that has been challenged by overlap between other cystic renal neoplasms, most notably with cystic nephroma. We report the first case of a bilateral mixed epithelial stromal tumor occurring in a 41-year-old dialysis-dependent woman, notably also the first case reported in a patient with end-stage renal disease. The neoplasms occurred 5 years apart and were diagnosed as mixed epithelial stromal tumor in both instances. We describe the presentation and pertinent radiologic, histologic, and immunophenotypic findings of these neoplasms with a review of the current debate regarding mixed epithelial stromal tumor and cystic nephroma taxonomy.

Editorial Comment on: Cystic Nephroma and Mixed Epithelial and Stromal Tumour of the Kidney: Opposite Ends of the Spectrum of the Same Entity?

the first two cases with a fatal clinical outcome. Histopathology 2004;44:302–4. [30] Yap YS, Coleman M, Olver I. Aggressive mixed epithelialstromal tumour of the kidney treated with chemotherapy and radiotherapy. Lancet Oncol 2004;5:747–9. [31] Svec A, Hes O, Michal M, Zachoval R. Malignant mixed epithelial and stromal tumor of the kidney. Virchows Arch 2001;439:700–2. [32] Jevremovic D, Lager DJ, Lewin M. Cystic nephroma (multilocular cyst) and mixed epithelial and stromal tumor of the kidney: a spectrum of the same entity? Ann Diagn Pathol 2006;10:77–82. [33] Omar AM, Khattak AQ, Lee JA. Cystic renal cell carcinoma arising from multilocular cystic nephroma of the same kidney. Int Braz J Urol 2006;32:187–9. [34] Shen SS, Truong LD, Ayala AG, Ro JY. Recently described and emphasized entities of renal neoplasms. Arch Pathol Lab Med 2007;131:1234–43. [35] Brown JM. Cystic partially differentiated nephroblastoma. J Pathol 1975;115:175–8. [36] Joshi VV, Banerjee AK, Yadav K, Pathak IC. Cystic partially differentiated nephroblastoma: a clinicopathologic entity in the spectrum of infantile renal neoplasia. Cancer 1977; 40:789–95. [37] Joshi VV, Beckwith JB. Pathologic delineation of the papillonodular type of cystic partially differentiated nephroblastoma. A review of 11 cases. Cancer 1990;66:1568–77. [38] Eble JN. Cystic nephroma and cystic partially differentiated nephroblastoma: two entities or one? Adv Anat Pathol 1994;1:99–102. [39] Kirkali Z, Algaba F, Scarpelli M, Trias I, Selvaggi FP, Van Poppel H. What does the urologist expect from the pathologist (and what can the pathologists give) in reporting on adult kidney tumour specimens? Eur Urol 2007;51: 1194–201. [40] Ljungberg B, Hanbury DC, Kuczyk MA, et al., European Association of Urology Guideline Group for renal cell

Epithelial-stromal tumor of seminal vesicle in a patient with chromophobe renal cell carcinoma and small lymphocytic lymphoma

Biphasic tumors of the seminal vesicle are rare. We report a further case in a 61-year-old man of a seminal vesicle epithelial-stromal tumor with focally atypical epithelial and stromal cells, the latter displaying a smooth muscle immunophenotype. In addition, this was associated with 2 synchronous malignant neoplasms, chromophobe renal cell carcinoma and small lymphocytic lymphoma, both of which were detected incidentally after clinical presentation because of the seminal vesicle mass.

Diagnostic Utility of WT1 Immunostaining in Ovarian Sertoli Cell Tumor

WT1, the Wilms tumor gene product, can be expressed in various tumors from different anatomic sites, including some types of ovarian tumors. Regarding the latter, most studies have focused on surface epithelial-stromal tumors in which serous carcinomas are usually positive and endometrioid carcinomas are negative. Very few studies have specifically investigated this marker in ovarian sex cord-stromal tumors; however, limited data in the literature suggest that WT1 may be frequently expressed in sex cord-stromal tumors. As pure Sertoli cell tumor can be in the histologic differential diagnosis of endometrioid tumors (particularly borderline tumor and carcinoma) and carcinoid, immunostaining for WT1 might be of diagnostic value. Immunohistochemical staining for WT1 was performed in 108 ovarian tumors: pure Sertoli cell tumor (n=26), endometrioid borderline tumor (n=25), classic well-differentiated endometrioid carcinoma (n=23), sertoliform endometrioid carcinoma (n=12), and carcinoid (n=22). Additionally, inhibin and calretinin immunostaining were performed in all cases of Sertoli cell tumor for purposes of comparing expression with WT1. Extent of immunostaining was scored on a 0 to 4+ semiquantitative scale, and immunohistochemical composite scores based on a combination of extent and intensity of immunostaining were calculated in positive cases (possible range, 1 to 12). Nuclear expression of WT1 was present in 96% of Sertoli cell tumors, 16% of endometrioid borderline tumors, 13% of classic well-differentiated endometrioid carcinomas, 25% of sertoliform endometrioid carcinomas, and 0% of carcinoids. In Sertoli cell tumors, expression was diffuse (>50% of positive cells) in all positive cases. When positive in the non-Sertoli cell tumors, the extent of expression tended to be focal to patchy (50% or less positive cells). In Sertoli cell tumors, inhibin and calretinin were expressed in 96% and 54% of cases, respectively. The extent of expression of inhibin tended to be diffuse, similar to WT1; however, the extent of immunostaining for calretinin tended to be focal to patchy. The immunohistochemical composite scores for WT1, inhibin, and calretinin were 11.2, 7.6, and 4.8, respectively. Coordinate patterns for the extent of expression of WT1, inhibin, and calretinin in pure Sertoli cell tumor showed that all 3 markers were positive in 54% of cases; however, 42% were positive for WT1 and inhibin but negative for calretinin. In cases positive for both WT1 and inhibin, expression of both markers was diffuse in 84% of cases, but WT1 was diffuse while inhibin was focal to patchy in 16% of cases. We conclude that ovarian Sertoli cell tumor should be added to the growing list of WT1-positive tumors. This marker is useful for the distinction of Sertoli cell tumor from endometrioid tumors and carcinoid. The diagnostic utility of WT1 in Sertoli cell tumor is similar to inhibin but better than that of calretinin.

Malignant mixed epithelial and stromal tumor of the kidney with rhabdoid features: report of a case including immunohistochemical, molecular genetic studies and comparison to morphologically similar renal tumors

Mixed epithelial stromal tumor of the kidney (MEST)/adult cystic nephroma (CN) is a lesion characterized by epithelial lined tubular or cystic structures interspersed within a variably prominent, distinctive spindle-cell stroma. Although typically benign, cases with malignant features have been reported. Herein, we report a MEST/CN with malignant stromal features and rhabdoid differentiation arising in the left kidney of an 84-year-old woman. Histologically, the tumor displayed multiple tubules and variably sized cystic structures lined by benign epithelium with an intervening malignant-appearing spindle-cell stroma. The malignant stroma displayed condensation in the regions surrounding the epithelial component consistent with the ovarian-like stroma typically observed in MEST/CN. In addition, the stromal cells displayed extensive rhabdoid differentiation. Immunohistochemical analysis revealed strong expression of cytokeratin 7, CAM 5.2, AE1/AE3, wide-spectrum keratin, and epithelial membrane antigen by the epithelial component. The stromal component displayed strong immunohistochemical expression of WT-1, CD-99, CD-56, INI1, and estrogen receptor; focal actin positivity; and was negative for desmin, myogenin, and progesterone receptor. Analysis by reverse transcriptase polymerase chain reaction failed to identify the SYT-SSX1 or SYT-SSX2 fusion transcripts characteristic of synovial sarcoma. To our knowledge, this represents the first report in the literature of malignant MEST with rhabdoid features and suggests that this entity should be considered in the diagnosis of renal stromal malignancies with prominent rhabdoid features.

Mixed epithelial and stromal tumor of the kidney in a puerperal woman

Puerperal pyrexia is still rampant, especially in third world countries, and is usually due to puerperal sepsis, urinary tract infections, upper respiratory infection, and breast infection. Rarely, in third world countries like India, it may be due to tuberculosis, malaria, typhoid, and so on, which are also rampant in the general population. Mixed epithelial and stromal tumor of the kidney (MESTK) is a recently recognized subset of renal tumors composed mainly of smooth muscle cells in which epithelial structures are embedded. It usually occurs in middle aged and older women. In the present case report, a 36-year-old woman presented with puerperal pyrexia, possibly due to tuberculosis and with an incidental mixed epithelial and stromal tumor of the kidney causing complex ascitis and fever, which required nephrectomy that was followed by full recovery. This case report highlights the importance of keeping MESTK in mind even in younger women with asymptomatic renal mass. It also highlights the importance of keeping renal tumors in mind as a possibility and to perform proper investigations for adequate treatment and recovery.

Assessment of gynecological malignancies based on pathologic reports in five general hospitals in Tehran (1995–2005)

5550 Background: Various histological types of gynecological tumors may develop from different etiological aspects. The observed differences in cancer incidence are mainly due to different individual and social risk factors. Step toward establishing a nation wide registry is being taken in this study. Methods: To give a relative frequency of female genital tract malignant tumors in Iran we designed a cross-sectional study included 450 women with definite diagnosis of gynecological cancer based on pathologic reports in five pathologic centers, Iran University of Medical sciences, Tehran, 1995–2005. WHO classification of gynecological tumors and International Federation of Gynecology and Obstetrics (FIGO) were used as basis of study. Spss 14 and correlation test was used for data analysis. Results: The average age of diagnosis was (50±0.7). 49.6% were menopausal. 82.7% were multipar. 89.8% were nonsmoker. 9.3% had history of using OCP. Ovarian cancers (55.5%), uterus cancers (24.9%) and cervical cancers (19.6%) were diagnosed. Surface epithelial-stromal tumor was the most frequent type of ovarian tumors (78.4%). Endometrial adenocarcinoma (70.5%) and squamous cell carcinoma (83%) were most frequent types of uterus and cervical cancers respectively.Well differentiated tumors were seen in 45%, 37% and 36% of uterus, cervical and ovarian tumors. In tumors of uterus and cervix the most frequent stage of diagnosis was stage IIA. The most metastatic diagnosed cases were seen between ovarian tumors (39.7%). Conclusions: Comparison with data published as review articles in NEJM till 2006, the most frequent gynecologic cancer in our study (ovarian cancer) is different to them; also the median age of our patients is lower than them. [Table: see text] No significant financial relationships to disclose.

Synchronous Sertoli Cell and Serous Cystadenoma Tumors of the Ovaries with Mixed Epithelial and Stromal Tumor of the Kidney: A Case Report

We present a rare case of a 68-year-old postmenopausal woman with a mobile, hard, and painless pelvic abdominal mass that was palpated to the umbilical scar. Ultrasonography demonstrated a solid mass in the upper pole of the right kidney and a predominantly solid pelvic abdominal mass. Serum testosterone was 413 ng/dL. The patient underwent laparotomy on the renal tumor, which was thought to have a probable ovarian metastasis. Bilateral ovariectomy and right nephrectomy were performed. Immunohistochemical and histopathologic assessment identified a right ovarian Sertoli cell tumor, a left ovarian serous cystadenoma, and a mixed epithelial-stromal tumor in the kidney with positive hormonal receptor. Because our patient had an ovarian neoplasm producing steroids and a kidney tumor expressing hormonal receptors, the hypothesis of possible endocrine dependence in the pathogenesis of mixed epithelial stromal tumor is reinforced.

Immunhistochemische Keimstrangmarker

Sex cord markers comprise proteins and hormones that are produced in sex cord-derivatives in normal ovaries and testes as well as in gonadal sex cord-stromal tumors. Sex cord markers (e.g. inhibin-alpha) are used clinically as serum tumor markers. Immunohistochemical staining of sex cord markers may be helpful in the differential diagnosis of ovarian sex cord-stromal tumors versus surface epithelial-stromal tumors, germ cell tumors, other ovarian tumors, and ovarian metastases. Inhibin-alpha has been shown to be the most specific marker of sex cord differentiation. In comparison, calretinin is a somewhat more sensitive albeit less specific marker. Currently, an immunohistochemical panel including inhibin-alpha and calretinin is considered most helpful in the differential diagnosis of ovarian sex cord-stromal tumors. CD99, Müllerian inhibiting substance (MIS), melan A and CD10, being sex cord markers of limited sensitivity and specificity, should only be used as part of an antibody panel in specific diagnostic settings. EMA, CK7 and chromogranin are considered additional markers that may be useful in the differential diagnosis of ovarian sex cord-stromal tumors.

Malignancy Arising in Seminal Vesicles in the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) Model

BACKGROUND Transgenic adenocarcinoma of mouse prostate (TRAMP) mice, derived by prostate specific expression of SV40 large T antigen using the rat probasin promoter, all develop prostate tumors akin to human prostate cancers. More recently, epithelial–stromal (ES) tumors resembling phyllodes tumors have been described in the seminal vesicles of TRAMP mice. We report malignancy arising in these ES tumors of the seminal vesicles in TRAMP mice. METHODS H&E stained sections from 28-week-old TRAMP mice autopsies were examined. Immunostains (cytokeratin, vimentin, desmin, and MIB-1) and electron microscopy were performed on selected blocks of the genitourinary system and metastatic tumor nodules. RESULTS The seminal vesicles frequently develop tumors containing broad papillae, with bland epithelium and a cellular spindled stroma just beneath the epithelium. The stromal cells have high nuclear to cytoplasmic ratio, frequent apoptotic cells and mitoses. In some cases, the stromal cells become large mass lesions that overgrow the prostate. The epithelium can also proliferate and become malignant. The tumors have high proliferation indices by MIB-1. Some metastatic tumors have characteristics similar to the seminal vesicle ES tumor. CONCLUSIONS Metastatic tumors in TRAMP mice show three patterns: (1) A definite adenocarcinoma pattern metastatic from the prostate; (2) poorly differentiated tumor without epithelial differentiation; (3) carcinosarcomatous pattern. The carcinosarcomatous pattern and some of the poorly differentiated tumors likely arise from seminal vesicle ES tumors. Prostate 69: 755–760, 2009. © 2009 Wiley-Liss, Inc.

The mixed epithelial stromal tumor of the kidney: A recently recognized entity

The mixed epithelial stromal tumor of the kidney: A recently recognized entity

Patterns and Progress in Ovarian Cancer Over 14 Years

To estimate the change in survival rates of women with ovarian cancer during the past 14 years. Women diagnosed with epithelial, germ cell, sarcomas, and sex-cord stromal ovarian tumors were identified from the Surveillance Epidemiology and End Results Database. Demographic and clinicopathologic factors, and survival information were extracted and tested using chi 2 and Kaplan-Meier and Cox regression analyses. A total of 30,246 women were diagnosed with ovarian cancer, including 26,753 non-clear cell epithelial, 1,411 clear cell, 818 sarcoma, 778 germ cell, and 486 sex-cord stromal tumors. The 5-year disease-specific survival rate across 1988-1992 and 1993-1997 improved from 45.4% to 48.6% (P < .001). The corresponding estimates show increases for non-clear cell epithelial carcinoma from 42.5% to 45.8% (P < .001), and for sarcomas from 33.5% to 38.8% (P = .07). However, improvements were not observed in those with clear cell, 64.3% to 63.9% (P = .82), and sex-cord stromal, 89.7% to 85.7% (P = .18), tumors of the ovary. In multivariable analyses, younger age, early stage, favorable histologic cell types, low-grade tumors, standard surgery, and recent time interval from 1993-1997 were independent prognostic factors for improved survival. In this large population-based study, there has been some improvement in the overall survival of women with ovarian cancers during a 14-year period. However, new treatment strategies are warranted for those with epithelial cancer and sarcomas of the ovary, given their overall poor prognosis. These results from our updated analyses might help to counsel women diagnosed with ovarian cancers.

Epithelial stromal tumor of the seminal vesicle

Primary tumors of the seminal vesicles are rare neoplasms; there have been only 69 accepted cases. The histologic features are usually adenocarcinoma; however, there are rarely reported epithelial stromal tumors of the seminal vesicles. We report a case of a 70-year-old man with an epithelial stromal tumor of the seminal vesicle who presented without symptoms of bladder outlet obstruction. The patient underwent radical cystoprostatectomy. No signs of tumor recurrence were noted within 14 months of surgery. To our knowledge, 13 cases of epithelial stromal tumors of the seminal vesicle have been previously reported.

Angiomyolipoma With Epithelial Cysts (AMLEC)

Renal angiomyolipoma (AML) is typically a solid lesion, composed of varying amounts of adipose, vascular, and muscular tissue, lacking an epithelial component. Although it is known that entrapped renal tubules may be observed in AML, presentation as a cystic mass has not been previously reported. We report the clinicopathologic and immunohistochemical features of four cystic renal AML. The lesions were found in 2 male and 2 female patients, ranging in age from 37 to 76 years, none with a history of hormonal therapy. One of the four patients had known tuberous sclerosis, and this patient and 1 other presented with bilateral cystic renal lesions. Grossly, the lesions measured between 1.3 and 4.5 cm in greatest dimension. Histologically, the lesions were each composed of three components: 1) epithelial cysts lined by cuboidal to hobnail cells; 2) a compact subepithelial "cambium-like" layer of cellular, müllerian-like AML stroma with prominent admixed chronic inflammation; and 3) muscle-predominant AML with associated dysmorphic blood vessels exterior to the cellular subepithelial stroma. Immunohistochemically, the stromal components of all four lesions labeled with HMB-45 and Melan-A, most intensely in the cellular subepithelial stroma, whereas smooth muscle actin and desmin demonstrated the opposite pattern, with greatest intensity in the muscle-predominant AML areas. Immunoreactivity for estrogen and progesterone receptors (ER, PR) and CD10 was present in all cases, with strongest and most diffuse staining in the subepithelial AML cells. The cyst lining cells were positive for pancytokeratin and soy bean agglutinin (the latter characteristic of distal nephron epithelium) but did not label for ER, PR, or melanocytic markers. Although these distinctive lesions may be confused with mixed epithelial-stromal tumor, their lack of female predominance or association with hormone therapy, their distinctive dysplastic blood vessels and disorganized exterior muscular layer, along with their immunohistochemical profile, support their classification as AML with epithelial cysts. Whereas the cysts appear to arise primarily from entrapped collecting ducts, the peculiar subepithelial condensation of AML stromal cells, with morphologic and immunohistochemical features suggesting differentiation toward endometrial stroma, may represent epithelial-induced müllerian differentiation not previously reported in AML.

Renal Cystic Diseases

This review aims to assist in the categorization of inherited, developmental, and acquired cystic disease of the kidney as well as to provide a pertinent, up-to-date bibliography. The conditions included are autosomal-dominant polycystic kidney disease, autosomal-recessive polycystic kidney disease, unilateral renal cystic disease (localized cystic disease), renal simple cysts, multicystic dysplastic kidney, pluricystic kidney of the multiple malformation syndromes, juvenile nephronophthisis and medullary cystic disease, medullary sponge kidney, primary glomerulocystic kidney disease, and glomerulocystic kidney associated with several systemic disorders mainly of genetic or chromosomal etiology, cystic kidney in tuberous sclerosis, and in von Hippel-Lindau syndrome, cystic nephroma, cystic variant of congenital mesoblastic nephroma, mixed epithelial stromal tumor of the kidney, renal lymphangioma, pyelocalyceal cyst, peripylic cyst and perinephric pseudocyst, acquired renal cystic disease of long-term dialysis, and cystic renal cell carcinoma and sarcoma. Whereas the gross and histologic appearance of some of these conditions may be diagnostic, clinical and sometimes molecular studies may be necessary to define other types.

Benign mixed epithelial stromal tumor of the renal pelvis with exophytic growth: case report

BackgroundMixed epithelial and stromal tumor (MEST) is a distinctive benign composite neoplasm of the kidney predominantly seen in females mostly in the perimenopausal period. Although these tumors are known to arise from renal pelvis, our case was distinct in that it had no intrapelvic component growing in exophytic fashion.Case reportA 35 year old female patient presented to us with vague abdominal pain. She had undergone excision of bilateral ovarian cystic masses for cystic teratoma twelve years earlier. A computed tomography scan of abdomen and pelvis showed a 9 × 7 cm uniformly solid mass with poor contrast enhancement situated in the inferomedial aspect of the left kidney. On exploration, the mass was arising from the inferior and anterior aspect of left renal pelvis, and was attached to it with a narrow pedicle. There was no adherence or attachment to the renal parenchyma. The mass was excised preserving the kidney. Microscopically, the tumor was composed of large collagenized areas containing bundles of spindle cells and several 'microcysts' lined by cuboidal epithelium suggestive of a benign mixed epithelial stromal tumor.DiscussionMixed epithelial tumors usually present in perimenopausal women as a partially cystic mass. Tumors are composed of irregular mixtures of cystic and solid areas, glands with variable complexity and distribution and the stromal component is characterized by a spindle cell proliferation. Commonly, it arises from the renal parenchyma and pelvis and nephrectomy is advocated to manage these tumors.ConclusionMEST is a distinctive benign tumor of the kidney that should be distinguished from other renal neoplasms. MEST arising from the renal pelvis and growing exophytically is a rare entity. The overall prognosis is favorable.

Incidental Stromal-Predominant Mixed Epithelial-Stromal Tumors of the Kidney: A Mimic of Intraparenchymal Renal Leiomyoma

Mixed epithelial-stromal tumor of the kidney is a recently recognized benign renal tumor that usually occurs in adult women and typically forms a sizable lesion with solid and cystic areas. The recognized morphologic spectrum of this recently described entity is evolving. To review the clinicopathologic features of 3 small mixed epithelial-stromal tumors of the kidney that were incidental findings in kidneys removed for other reasons. The clinical presentation and morphologic findings of the 3 cases were reviewed. A panel of immunohistochemical stains was performed. Academic medical center. All 3 lesions contained predominantly fascicles of smooth muscle mimicking leiomyoma, but they also had cellular subpopulations of smaller, müllerian-appearing stromal cells. Tubules present within the lesion were most abundant at the periphery, suggesting that they might be entrapped. Although only the spindled smooth muscle cells were immunoreactive for muscle markers desmin and actin, both the spindled smooth muscle cells and the cellular müllerian-appearing stromal cells demonstrated diffuse nuclear labeling for estrogen and progesterone receptors. Mixed epithelial-stromal tumor of the kidney may present as an incidental stromal-predominant lesion within the kidney. Such lesions are easily confused with leiomyomas or stromal-predominant angiomyolipomas.