Mixed epithelial and stromal tumor of the kidney

Using imaging to diagnose renal tumors beyond nephroblastoma

Wilm's tumor (WT) accounted for the vast majority of renal tumors in children (92%). However, there are many atypical or rare forms of kidney cancer, and it is certainly useful to have a diagnostic orientation in imaging to differentiate between the different diagnoses, guiding that way the therapeutic management. We report the cases of 3 patients who were initially diagnosed with nephroblastoma on the basis of radiological data (via PACS search), underwent pre-operative chemotherapy and then nephrectomy, and whose anatomopathological evidence came back in favor of benign renal tumors. Nephroblastoma is the most common renal tumor in children, but other benign tumors should not be neglected, radiological signs that may point to this entity should be taken into account, so that neoadjuvant chemotherapy with its enfeebling side effects can be avoided.

Estrogen Receptor Expression in DICER1-related Lesions is Associated With the Presence of Cystic Components

DICER1 tumor predisposition syndrome results from pathogenic variants in DICER1 and is associated with a variety of benign and malignant lesions, typically involving kidney, lung, and female reproductive system. Over 70% of sarcomas in DICER1 tumor predisposition syndrome occur in females. Notably, pediatric cystic nephroma (pCN), a classic DICER1 tumor predisposition syndrome lesion, shows estrogen receptor (ER) expression in stromal cells. There are also renal, hepatic, and pancreatic lesions unassociated with DICER1 tumor predisposition syndrome that have an adult female predominance and are characterized/defined by ER-positive stromal cells. Except for pCN, the expression of ER in DICER1-associated lesions remains uninvestigated. In the present study, ER expression was assessed by immunohistochemistry in 89 cases of DICER1-related lesions and 44 lesions lacking DICER1 pathogenic variants. Expression was seen in stromal cells in pCN and pleuropulmonary blastoma (PPB) types I and Ir, whereas anaplastic sarcoma of kidney and PPB types II and III were typically negative, as were other solid tumors of non-Müllerian origin. ER expression was unrelated to the sex or age of the patient. Expression of ER showed an inverse relationship to preferentially expressed antigen in melanoma (PRAME) expression; as lesions progressed from cystic to solid (pCN/anaplastic sarcoma of kidney, and PPB types I to III), ER expression was lost and (PRAME) expression increased. Thus, in DICER1 tumor predisposition syndrome, there is no evidence that non-Müllerian tumors are hormonally driven and antiestrogen therapy is not predicted to be beneficial. Lesions not associated with DICER1 pathogenic variants also showed ER-positive stromal cells, including cystic pulmonary airway malformations, cystic renal dysplasia, and simple renal cysts in adult kidneys. ER expression in stromal cells is not a feature of DICER1 perturbation but rather is related to the presence of cystic components.

Partial nephrectomy in multiple mixed epithelial and stromal tumors (MEST)

Mixed epithelial and stromal tumor (MEST) of the kidney is not a common diagnosis. This tumor usually mimics solid-cystic malignant renal tumors and most cases are treated surgically. Here, we presented a 35-year-old female with simultaneous two separate large solid-cystic masses with contrast enhancement in lower and upper pole of left kidney which were managed surgically via partial nephrectomy. Microscopic evaluation showed solid-cystic tumor with variably sized cysts lined by flattened to cuboidal epithelium that was compatible with MEST. Follow up evaluation revealed normal parenchymal renal tissue and proper function without any evidence of local recurrence.

Tumor-to-Tumor Metastasis of Lung Cancer to Kidney Cancer: A Review of the Literature and Our Experience

Tumor-to-tumor metastasis (TTM) is a rare phenomenon documented in patients with multiple primary cancers. This condition is defined as a metastasis between two true primary tumors. The most frequently reported recipient tumor is renal cell carcinoma (RCC), and the lung carcinomas are the most common metastatic tumor donors. Therefore, this paper attempts to address the current gap in knowledge about this rare phenomenon. The first part of this review outlines the recently proposed models and mechanisms involved in the TTM process. The second part then summarizes and analyzes previous case reports in the literature. We also present our experience with the case of lung cancer that metastasized into RCC. Given the sporadic incidence of TTM, no specific management guidelines exist. Therefore, considering TTM in patients with multiple primary tumors is important as it could potentially modify the oncological management offered.

Unmasking the Mystery of Renal Neoplasm in a Perimenopausal Woman: A Case Report

Mixed epithelial and stromal tumor (MEST) is a benign, complex, and rarely encountered renal neoplasm. This case involves a 46-year-old perimenopausal woman who presented with symptoms, such as abdominal pain, burning sensation during urination, increased urinary frequency, and hesitancy. Computed tomography (CT) urography revealed an exophytic, heterogeneously hyperdense mass originating from the interpolar and lower pole parenchyma of the left kidney, suggesting a neoplastic origin. Due to concerns about malignancy and the presence of local symptoms, a laparoscopic-assisted left radical nephrectomy was performed. Histopathological examination of the excised tissue revealed a biphasic neoplasm consisting of epithelial and stromal elements. The epithelial component exhibited cysts and glands of variable sizes, lined by columnar cells and surrounded by stromal tissue. The diagnosis of MESTs of the kidney was established and confirmed through immunohistochemistry. This unique type of benign kidney tumor can be effectively managed through conservative surgery and is associated with a favorable prognosis.

Mixed Epithelial Stromal Tumor of the Kidney With a Mesenteric Lymph Node: A Case Report and Literature Review

Mixed epithelial and stromal tumor (MEST) of the kidney belongs to the broad spectrum of renal neoplasms, distinguished by their varying composition of stromal to epithelial components. The histopathological display of the biphasic growth pattern of mesenchymal and epithelial elements, often with estrogen and progesterone receptor positivity, clinches the diagnosis. It is typically benign, with low recurrence rates and excellent prognosis after surgical resection. MEST constitutes a rare and unique subset, with limited research and understanding, requiring differentiation from other renal tumors. Our patient's presentation of a morphologically benign renal MEST with an imaging-positive inferior mesenteric lymph node renders this case exceptionally rare.

Cystic Renal Masses: Old and New Paradigms

Cystic renal masses describe a spectrum of lesions with benign and/or malignant features. Cystic renal masses are most often identified incidentally with the Bosniak classification system stratifying their malignant potential. Solid enhancing components most often represent clear cell renal cell carcinoma yet display an indolent natural history relative to pure solid renal masses. This has led to an increased adoption of active surveillance as a management strategy in those who are poor surgical candidates. This article provides a contemporary overview of historical and emerging clinical paradigms in the diagnosis and management of this distinct clinical entity.

Mixed epithelial and stromal tumor of the kidney: A retrospective clinicopathological evaluation

OBJECTIVE

Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare renal tumor for which there is limited clinical case experience. The aim of this study was to investigate the clinicopathological features, imaging manifestations, immunohistochemical phenotype, diagnosis, and differential diagnosis of MESTK.

METHODS

We systematically evaluated the clinicopathological characteristics of 13 patients diagnosed with MESTK from 2016 to 2022.

RESULTS

There were 12 female cases and 1 male case, and their age ranged from 24 to 62 (mean age 47 years). The tumor was located in the left kidney in 11 patients. Seven of these patients were located in the upper pole of the left kidney. The mean diameter of the tumor was 4.6 cm (range 1.3-8.6 cm), and the main body of the tumor was mainly located in the medulla or medulla. In 7 cases, the tumors were clearly outlined, 4 cases had clear but irregular borders, and in 3 cases, the masses broke through the renal capsule but did not invade the surrounding organs. All tumors had varying proportions of cystic and solid components. In most tumors, the epithelial cell component was predominant. Among the epithelial components, we observed a predominance of large cysts. Small cysts and tubular structures were also seen; the least common were papillary structures. The most common types of lining epithelium were flat and cuboidal. The cell cytoplasm was predominantly eosinophilic with hyaline degeneration. The tumor cells were composed of different proportions of sparse hypocellular areas and dense hypercellular areas between these cells. In most cases, the cellular stroma had an ovarian-like appearance. It is characterized histologically by mature adipocytes, thick-walled blood vessels, and chronic inflammatory cells. Calcification and collagenization were seen in a few cases. In all female patients, estrogen and progesterone receptors in the interstitial component were almost always positively expressed. In male patients, all interstitial components showed locally positive expression of androgens.

CONCLUSION

MESTK had unique characteristics with complex and variable lesion shapes. There was a high degree of overlap with cystic kidney cancer, and the rate of missed and misdiagnosis was extremely high. The diagnosis could not be confirmed by preoperative imaging. The final diagnosis depended on pathomorphology.

Malignant Mixed Epithelial and Stromal Tumor of the Kidney: Report of a Carcinosarcoma Case and an Updated Literature Review

Mixed epithelial and stromal tumors of the kidney (MESTK) are rare and recently defined entities that comprise both epithelial and stromal cells. MESTK is mostly benign; however, to date, 18 borderline or malignant cases have been reported. In this study, we report a case of carcinosarcoma exhibiting a large carcinoma and small sarcoma component, and review the relevant literature. The patient was a 59-year-old woman who presented with a large mass in the left kidney having solid and focal cystic components. The patient underwent left radical nephrectomy. The tumor was gray-white and solid-cystic, with a relatively clear boundary. Microscopically, the tumor revealed benign and malignant components. The benign component consisted of multiple tubules, variable-sized cysts lined with benign epithelium, and hyalinized stroma. The malignant component was composed of predominantly small cell neuroendocrine carcinoma and a small quantity of adenocarcinoma, squamous cell carcinoma, and sarcoma. Finally, a diagnosis of the malignant MESTK was made. Certain cases of borderline or malignant transformation of MESTK have been published, so it is important to enhance findings made by other studies.

Mixed Epithelial and Stromal Tumor: A Rare Renal Neoplasm-Case Report with Clinicopathologic Features and Review of the Literature

Mixed epithelial and stromal tumor (MEST) is a rare benign renal neoplasm composed of epithelial and stromal components. Here, we report a 61-year-old woman presenting with a left complex cystic renal mass. The lesion was found incidentally on ultrasound for abdominal discomfort. CT scan and MRI showed a 7.4 cm complex cystic lesion in the left kidney. The differential diagnoses included complex renal cyst and cystic renal cell carcinoma. Laparoscopic nephrectomy showed a large 7.5 cm multicystic tumor with thick and thin septae and smooth walled-cysts containing clear watery fluid. Histologic examination showed variable sized cysts lined by flattened, cuboidal to columnar epithelium with focal hobnailing. No significant cytologic atypia or mitoses were noted. The cyst lining epithelium was positive for CK7 and high molecular weight cytokeratin (34Be12). The stroma was positive for alpha smooth muscle actin, CD10, estrogen receptor, and progesterone receptor. This report contributes an additional case to our collective knowledge of these lesions and summarizes the literature around these rare neoplasms.

Cystic Kidney Diseases That Require a Differential Diagnosis from Autosomal Dominant Polycystic Kidney Disease (ADPKD)

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary cystic kidney disease, with patients often having a positive family history that is characterized by a similar phenotype. However, in atypical cases, particularly those in which family history is unclear, a differential diagnosis between ADPKD and other cystic kidney diseases is important. When diagnosing ADPKD, cystic kidney diseases that can easily be excluded using clinical information include: multiple simple renal cysts, acquired cystic kidney disease (ACKD), multilocular renal cyst/multilocular cystic nephroma/polycystic nephroma, multicystic kidney/multicystic dysplastic kidney (MCDK), and unilateral renal cystic disease (URCD). However, there are other cystic kidney diseases that usually require genetic testing, or another means of supplementing clinical information to enable a differential diagnosis of ADPKD. These include autosomal recessive polycystic kidney disease (ARPKD), autosomal dominant tubulointerstitial kidney disease (ADTKD), nephronophthisis (NPH), oral-facial-digital (OFD) syndrome type 1, and neoplastic cystic kidney disease, such as tuberous sclerosis (TSC) and Von Hippel-Lindau (VHL) syndrome. To help physicians evaluate cystic kidney diseases, this article provides a review of cystic kidney diseases for which a differential diagnosis is required for ADPKD.

Differentiating the clinical and computed tomography imaging features of mixed epithelial and stromal tumors of the kidney to establish a treatment plan

Objective

To differentiate the clinical features and computed tomography imaging features in the two types of mixed epithelial and stromal tumor of the kidney (MESTK) and to establish a treatment plan for the MESTK types.

Methods

Seventeen patients who underwent multidetector computed tomography (MDCT) before surgery and had a pathological diagnosis of MESTK were enrolled. Their clinical information (R.E.N.A.L. nephrometry score (R.E.N.A.L.‐NS), radical nephrectomy (RN), partial nephrectomy (PN), etc.) were collected. The radiological features included renal sinus fat invagination (SFI), maximal diameter (MD), capsule and septa of the tumor, etc., were also analyzed. They were divided into two types according to the MD_solid/MD_tumor ratio (solid type with >60%; cystic type with ≤60%). An independent‐sample t‐test and Fisher exact test were used to assess the differences between the two groups.

Results

MESTKs demonstrated a variable multi‐septate cystic and solid components with a delayed enhancement. There were nine patients for solid type and eight patients for cystic type. Compared with solid type, the lesions in cystic type have larger MD (81.00 ± 37.91 vs. 41.22 ± 24.19, p = 0.020), higher R.E.N.A.L.‐NS (10.03 ± 0.50 vs. 8.95 ± 1.26, p < 0.001), higher RN (75.00% vs. 22.22%, p = 0.015), larger SFI (87.5% vs. 33.3%, p = 0.05), more septa (100% vs. 0%, p < 0.001), and more capsule (100% vs. 11.1%, p < 0.001).

Conclusion

Cystic type MESTK has more hazardous features (such as larger MD, higher R.E.N.A.L.‐NS, more RN, greater SFI, multiple septa) compared with solid type, suggesting that RN is more suitable for cystic type and PN for solid type.

Mixed epithelial and stromal tumor (MEST) in a young adult male: A case report and literature review

Introduction and importance

A MEST is a rare renal tumor, with stromal as well as epithelial components. It is predominantly benign and local recurrence is not very common. In the majority of the cases, it occurs in females. Its occurrence in a young male makes it a rarity.

Case presentation

A 24 years old male presented at SIUT with the complaint of left flank pain on and off for one month. CT scan showed soft tissue density mass in left renal pelvis extending from mid-pole calyces to pelviuretric junction, leading to obstruction and ultimately mild uropathy. We found a partially obstructing staghorn calculus with asymmetrical cortical thinning. Left Robot-Assisted Nephro-ureterectomy plus excision of bladder cuff was planned in which 3 × 4 cm mass involving the left renal pelvis was excised. To date, there is no radiologic evidence of disease recurrence.

Clinical discussion

MEST in young adults is an extremely rare tumor. They have been referred to by many alternate synonyms including 'adult mesoblastic nephroma' and 'cystic nephroma' with 'ovarian' or 'cellular' type stroma. Majority of patients with MEST present, with hematuria, abdominal pain, palpable flank mass, recurrent urinary tract infections. Similarly, our patient presented initially with nonspecific pain in the left flank region. Majority of cases in the literature presented with the tumor in benign stage, with localized spread, and without recurrence.

Conclusion

Mixed epithelial and stromal tumors (MEST) of the kidney are distinct entities of benign kidney tumors. MEST in young males is a very rare entity, and a small number of cases exist. Histopathology plays a very cardinal role in diagnosis, and overall the disease has a promising outcome with conservative surgery.

Sex and Gender Differences in Kidney Cancer: Clinical and Experimental Evidence

Simple Summary

Kidney cancer is a frequent malignant tumor that accounts for approximately 5% of all cancer incidences. It affects both males and females, but males are twice as likely to develop kidney cancer than females. Evidence shows that this discrepancy takes root in individual differences, such as genetics or pathologies that affect the patient. It is then reflected in the clinical characteristics of the tumors, as males have larger and more aggressive tumors. Understanding the sex- and gender-based differences in kidney cancer is essential to be able to offer patients individualized medicine that would better cover their needs in terms of prevention, diagnosis and treatment.

Abstract

Sex and gender disparities have been reported for different types of non-reproductive cancers. Males are two times more likely to develop kidney cancer than females and have a higher death rate. These differences can be explained by looking at genetics and genomics, as well as other risk factors such as hypertension and obesity, lifestyle, and female sex hormones. Examination of the hormonal signaling pathways bring further insights into sex-related differences. Sex and gender-based disparities can be observed at the diagnostic, histological and treatment levels, leading to significant outcome difference. This review summarizes the current knowledge about sex and gender-related differences in the clinical presentation of patients with kidney cancer and the possible biological mechanisms that could explain these observations. Underlying sex-based differences may contribute to the development of sex-specific prognostic and diagnostic tools and the improvement of personalized therapies.

Key Renal Neoplasms With a Female Predominance

Renal neoplasms largely favor male patients; however, there is a growing list of tumors that are more frequently diagnosed in females. These tumors include metanephric adenoma, mixed epithelial and stromal tumor, juxtaglomerular cell tumor, mucinous tubular and spindle cell carcinoma, Xp11.2 (TFE3) translocation-associated renal cell carcinoma, and tuberous sclerosis complex (somatic or germline) associated renal neoplasms. The latter category is a heterogenous group with entities still being delineated. Eosinophilic solid and cystic renal cell carcinoma is the best-described entity, whereas, eosinophilic vacuolated tumor is a proposed entity, and the remaining tumors are currently grouped together under the umbrella of tuberous sclerosis complex/mammalian target of rapamycin-related renal neoplasms. The entities described in this review are often diagnostic considerations when evaluating renal mass tissue on biopsy or resection. For example, Xp11.2 translocation renal cell carcinoma is in the differential when a tumor has clear cell cytology and papillary architecture and occurs in a young or middle-aged patient. In contrast, tuberous sclerosis complex-related neoplasms often enter the differential for tumors with eosinophilic cytology. This review provides an overview of the clinical, gross, microscopic, immunohistochemical, genetic, and molecular alterations in key renal neoplasms occurring more commonly in females; differential diagnoses are also discussed regardless of sex predilection.

Cystic nephroma treated with nephron-sparing technique: A case report

Multilocular cystic nephroma is a rare benign kidney tumor, which is typically characterized by a unilateral, multicystic renal mass without solid elements. Cystic nephroma has a bimodal distribution and two-thirds of tumors involve children aged between 3 months and 2 years, with male predominance; a second peak affects the age group >30 years old, in which females are predominantly affected. The incidence rate for this rare tumor in patients aged 5-30 years is only 5%. The present study reports a case of a 31-year-old woman affected by a multilocular cystic nephroma in the upper pole of the right kidney, with direct tumor extension into the renal pelvis through a calyx. After a partial nephrectomy on the patient, the pathological examination confirmed a multilocular cystic nephroma in the right renal specimens.

Mesenteric and Retroperitoneal Mucinous Cystic Neoplasms: A Case Series

Aims. Mucinous cystic neoplasms (MCNs) are cystic neoplasms with mucinous epithelium surrounded by ovarian-like stroma. Extraovarian MCN occurring in the liver and pancreas have been well characterized. However, only rare case reports of MCN arising outside of these locations have been reported. MCNs arising in unusual locations should enter the differential diagnosis of mucinous intra-abdominal tumors and must be distinguished from more common mimics. Therefore, we aimed to examine a series of MCNs of the retroperitoneum and mesentery to characterize the clinicopathologic features of this entity. Methods and results. Seven MCNs arising in the abdominal mesentery or retroperitoneum were retrospectively identified. A clinicopathologic, histologic, and immunohistochemical (keratin 7, keratin 19, keratin 20, calretinin, inhibin-α, steroidogenic factor-1 (SF-1), estrogen receptor (ER), progesterone receptor (PR), PAX8, CDX2, and CD10) analysis was performed. All 7 MCNs were from females with a median age of 41 years old and a median size of 8 cm. All cases demonstrated mucinous with or without concomitant non-mucinous epithelium overlying spindle cell ovarian-like stroma. Luteinized cells were noted. The epithelium was positive for keratin 7 and keratin 19 in all 7 cases, while the stroma expressed ER, PR, and SF-1 in all cases stained. Calretinin was focally positive in the stroma of 3 of 7 cases, while inhibin-α was focally expressed in 5 of 6 cases. Conclusions. These results highlight the clinicopathologic, histologic, and immunophenotypic similarities between MCNs of the mesentery, retroperitoneum, pancreas, and liver. Overlapping features suggest a common histogenesis for all MCNs, which could include periductal fetal mesenchyme, aberrant migration of primordial germ cells, or abnormal differentiation or metaplasia of the embryonic coelomic epithelium.

A MEST up classification? Review of the re-classification of mixed epithelial and stromal tumor and adult cystic nephroma for the abdominal radiologist

Mixed epithelial and stromal tumor (MEST) and the tumor formerly known as adult cystic nephroma (ACN) are uncommon renal tumors that have historically been described as separate entities in terms of histologic and imaging findings. However, these entities share many epidemiologic, radiologic, and pathologic features. While recent surgical and pathological literature has supported classifying MEST and ACN within the same tumor family, most radiologists and radiology texts continue to describe MEST and ACN as separate entities.

Radiologic features of mixed epithelial and stromal tumors of the kidney: Hyperattenuating on unenhanced computed tomography and T2-hypointensity on magnetic resonance imaging

In the 2016 World Health Organization renal tumor classification, the mixed epithelial and stromal tumor family was introduced as a new entity. This family encompasses a spectrum of tumors, ranging from predominantly cystic tumors (adult cystic nephromas) to tumors that are variably solid (mixed epithelial and stromal tumors). The majority of previous studies incorporating “mixed epithelial and stromal tumor” in the titles were actually reports of imaging findings of adult cystic nephroma. Thus, the solid component of mixed epithelial and stromal tumors has not been well evaluated. In this study, we present 2 cases of mixed epithelial and stromal tumors, as defined by the 2016 World Health Organization classification, showing a predominantly solid component. The characteristic findings of the solid component of these tumors were T2-hypointensity on magnetic resonance imaging and hyperattenuation on unenhanced computed tomography. Angiomyolipoma with epithelial cysts and epithelioid angiomyolipoma should be considered in the differential diagnosis of mixed epithelial and stromal tumors.

Molecular and Immunohistochemical Analysis of Mucinous Cystic Neoplasm of the Liver

OBJECTIVES

Mucinous cystic neoplasm of the liver is characterized by neoplastic mucinous and/or biliary epithelium surrounded by ovarian-type stroma. Immunohistochemical studies have shown that the ovarian-type stroma expresses estrogen receptor, suggesting potential hormonal responsiveness. The molecular biology of mucinous cystic neoplasm of the liver remains poorly studied.

METHODS

Transcriptome sequencing and immunohistochemistry were performed on a series of mucinous cystic neoplasms.

RESULTS

Mucinous cystic neoplasm of the liver exhibited significantly increased RNA expression of ovarian stromal markers WT1, PR, and ER2 and sex cord stromal markers SF-1, inhibin-α, and calretinin compared with nonneoplastic liver. Immunohistochemistry confirmed the RNA-level data. Evidence for sex hormone biosynthesis was identified by significant overexpression of multiple estrogen biosynthetic enzymes. Expression of 17β-hydroxysteroid dehydrogenase 1 was confirmed immunohistochemically. Pathway analysis also identified significant upregulation of the hedgehog and Wnt pathways and significant downregulation of T-helper 1 and T-helper 2 pathways.

CONCLUSIONS

Mucinous cystic neoplasm of the liver recapitulates ovarian stroma at the morphologic, DNA, RNA, and protein levels. These data support the concept that this tumor likely arises from ectopic primitive gonadal tissue and/or stromal cells with capacity to transdifferentiate to ovarian cortical cells.

Renal epithelial and stromal tumor with a multiple cystic lesion localized in the upper portion of the right kidney

A 60-year-old Japanese woman was admitted because of the polycystic mass with right flank pain localized in the upper portion of the right kidney. Right nephrectomy was performed because the mass lesion had continuously increased in size over the past 10 years. A surgical specimen showed histology consistent with a mixed epithelial and stromal tumor, which is closely related to multilocular cystic nephroma, and was diagnosed by a defined capsule between the cystic mass lesion and normal renal tissue by CT and MRI, and histology. Localized renal cystic disease that does not have a capsule was excluded from differential diagnosis.

Imaging of mixed epithelial and stromal tumor of the kidney: A case report and review of the literature

BACKGROUND

Mixed epithelial and stromal tumors of the kidney (MESTKs) are a rare entity (about a hundred cases reported). They occur almost exclusively in postmenopausal women, with only seven cases reported in men. As this entity is very rare, little is known on its imaging features, especially magnetic resonance imaging (MRI) findings. In women, at MRI, the cystic component shows T1 hypointensity and T2 hyperintensity, while the solid component shows T1 hyperintensity and T2 hypointensity.

CASE SUMMARY

We report the computed tomography (CT) and MRI findings of MESTK in a 19-year-old male adolescent. To our knowledge, this case report is the first report of MRI findings of MESTK in male adolescents. The patient was admitted to Subei People's Hospital (Jiangsu Province, China) in July 2017 after a renal mass on the left side was detected by ultrasound during a clinical examination. Blood tests were all normal. Non-enhanced CT showed a round, well-circumscribed complex mass, approximately 45 mm × 40 mm in size. MRI revealed a clear well-circumscribed mass with a mixed arrangement of solid and cystic components. On T2 weighted images, some hypointensities were found in the solid areas. After contrast enhancement, moderate or mild enhancement was found in the solid component, which increased with time. A radical left nephrectomy was performed. The pathology analysis revealed a mixed epithelial and stromal tumor. The patient had no imaging findings of recurrence or metastasis at 12 months following surgery.

CONCLUSION

The possibility of MESTK should be considered in male adolescents. MRI can provide useful information for the preoperative diagnosis.

Imaging of Unusual Renal Tumors

PURPOSE OF REVIEW

Renal masses are a wide entity and a common finding in clinical practice. Detection of these masses has increased in the last years, yet mortality rates have slightly decreased.

RECENT FINDINGS

According to the World Health Organization classification, there are 8 types, 51 subtypes, and a lot more subsequent subclassifications of renal tumors. Histopathological analysis should always be assessed for final diagnosis of theses tumors. However, imaging can be an important diagnostic guidance. The most common diagnoses of renal tumor are clear cell carcinoma, papillary renal cell carcinoma, angiomyolipoma, and transitional cell carcinoma. Nonetheless, a considerable variety of particular tumors can arise from the kidney, challenging the expertise of radiologists and urologists on this subject. The awareness of these unusual entities is vital for professionals working at a complex medical facility with greater volume of patients. We hereby present uncommon renal tumors and its pathological and radiological features.

Classification and Diagnosis of Cystic Renal Tumors: Role of MR Imaging Versus Contrast-Enhanced Ultrasound

Superior soft tissue and contrast resolution of MR imaging benefits sensitivity to kidney cyst features and classification, which may have an impact on patient management and outcomes. Contrast-enhanced ultrasound (CEUS) may have nearly similar sensitivity for detection of cyst features yet is dependent on patient body habitus and adequacy of visualization windows for the kidneys, which does not have the same impact on MR imaging results. Both MR imaging and CEUS may provide superior kidney cyst assessment compared with contrast-enhanced CT; however, further research is needed, particularly for the identification of role of CEUS.

Mixed Epithelial and Stromal Tumor of the Kidney with Extension into Inferior Vena Cava: Case Report and Discussion of Adult Biphasic Cystic Renal Lesions and the Significance of Vascular Involvement

Mixed epithelial and stromal tumor (MEST) is a biphasic adult renal lesion composed of solid and cystic areas containing spindle cell stroma and epithelium that lines the tubules and cystic spaces. While most MEST lesions are benign, rare cases with malignant morphology and biology have been reported. We present a case of mixed epithelial and stromal tumor of the kidney (MEST) with extension into the inferior vena cava in a young adult male. We discuss the differential diagnosis of MEST in the context of other biphasic cystic renal lesions and the significance of vascular involvement in the setting of an otherwise benign tumor morphology.

Primordial germ cells as a potential shared cell of origin for mucinous cystic neoplasms of the pancreas and mucinous ovarian tumors

Mucinous ovarian tumors (MOTs) morphologically and epidemiologically resemble mucinous cystic neoplasms (MCNs) of the pancreas, sharing a similar stroma and both occurring disproportionately among young females. Additionally, MOTs and MCNs share similar clinical characteristics and immunohistochemical phenotypes. Exome sequencing has revealed frequent recurrent mutations in KRAS and RNF43 in both MOTs and MCNs. The cell of origin for these tumors remains unclear, but MOTs sometimes arise in the context of mature cystic teratomas and other primordial germ cell (PGC) tumors. We undertook the present study to investigate whether non-teratoma-associated MOTs and MCNs share a common cell of origin. Comparisons of the gene expression profiles of MOTs [including both the mucinous borderline ovarian tumors (MBOTs) and invasive mucinous ovarian carcinomas (MOCs)], high-grade serous ovarian carcinomas, ovarian surface epithelium, Fallopian tube epithelium, normal pancreatic tissue, pancreatic duct adenocarcinomas, MCNs, and single-cell RNA-sequencing of PGCs revealed that both MOTs and MCNs are more closely related to PGCs than to either eutopic epithelial tumors or normal epithelia. We hypothesize that MCNs may arise from PGCs that stopped in the dorsal pancreas during their descent to the gonads during early human embryogenesis, while MOTs arise from PGCs in the ovary. Together, these data suggest a common pathway for the development of MCNs and MOTs, and suggest that these tumors may be more properly classified as germ cell tumor variants. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Contemporary update on imaging of cystic renal masses with histopathological correlation and emphasis on patient management

This article presents an updated review of cystic renal mass imaging. Most cystic renal masses encountered incidentally are benign and can be diagnosed confidently on imaging and require no follow-up. Hyperattenuating masses discovered at unenhanced or single-phase enhanced computed tomography (CT) measuring between 20-70 HU are indeterminate and can be further investigated first by using ultrasound and, then with multi-phase CT or magnetic resonance imaging (MRI); as the majority represent haemorrhagic/proteinaceous cysts (HPCs). Dual-energy CT may improve differentiation between HPCs and masses by suppressing unwanted pseudo-enhancement observed with conventional CT. HPCs can be diagnosed confidently when measuring >70 HU at unenhanced CT or showing markedly increased signal on T1-weighted imaging. Although the Bosniak criteria remains the reference standard for diagnosis and classification of cystic renal masses, histopathological classification and current management has evolved: multilocular cystic renal cell carcinoma (RCC) has been reclassified as a cystic renal neoplasm of low malignant potential, few Bosniak 2F cystic masses progress radiologically during follow-up; RCC with predominantly cystic components are less aggressive than solid RCC; and Bosniak III cystic masses behave non-aggressively. These advances have led to an increase in non-radical management or surveillance of cystic renal masses including Bosniak 3 lesions. Tubulocystic RCC is a newly described entity with distinct imaging characteristics, resembling a pancreatic serous microcystadenoma. Other benign cystic masses including: mixed epithelial stromal tumours (MEST) are now considered in the spectrum of cystic nephroma and angiomyolipoma (AML) with epithelial cysts (AMLEC) resemble a fat-poor AML with cystic components.

Malignant mixed epithelial and stromal tumour of the kidney: a case report and a literature review

Introduction.

Mixed epithelial and stromal tumour of the kidney (MEST) is a rare and distinctive neoplasm accounting for 0.2% of all renal cancers. Most of these tumours behave in a benign fashion but 13 cases with malignant transformation have already been reported. We present the first case of an extremely aggressive MEST with rapid recurrence after radical treatment, demonstrating objective response to chemotherapy.

Case presentation.

A 31-year-old female presented to the hospital complaining of gross hematuria. Computed tomography (CT) revealed an intraparenchymal mass in the left kidney forming a tumour thrombus in the inferior vena cava (IVC). Metastatic disease was ruled out and, under the clinical diagnosis of renal cell carcinoma, left radical nephrectomy with IVC thrombectomy was performed. The histopathological examination confirmed malignant MEST of the kidney. At the follow-up 12 months after surgery, a recurrent tumour in the left paravertebral area and a tumour thrombus in the IVC were detected. A second surgery was recommended and the mass from the paravertebral area was removed, so resection of the IVC with prosthetic replacement was performed. The histopathologic examination confirmed a recurrent malignant MEST. At the follow-up three months after the second surgery disease progression was diagnosed, so chemotherapy with ifosfamide and doxorubicin was initiated. The CT scan performed 14 months after the chemotherapy confirmed a stable process of the disease with no signs of progression.

Conclusions.

A literature review and our case report confirm the existence of extremely aggressive malignant MEST that shows response to chemotherapy. However, more reports are needed to improve our understanding about the biology of the MEST to develop any recommendations on personalized therapy.

Bilateral and multiple mixed epithelial and stromal tumors of the kidney: A case report

Mixed epithelial and stromal tumor (MEST) of the kidney is a benign tumor occurring predominantly in older women. Histologically, MEST comprises tubuloglandular and cystic structures in an ovarian-like stroma. Bilateral and multiple cases are rare. We herein present a case of bilateral and multiple MEST in a 43-year-old woman. The patient presented with gross hematuria and was referred to a primary care physician. A computed tomography scan revealed 5 tumors in the right and 2 in the left kidney. Renal cell carcinoma was suspected, and left partial nephrectomy followed by right radical nephrectomy was planned. After the left partial nephrectomy, the histopathological diagnosis was MEST, which was consistent with the results obtained following needle biopsy. Therefore, the contralateral tumor was also suspected to be MEST, and needle biopsy was performed. The histopathological diagnosis was identical and the right kidney was spared. The patient is currently periodically monitored. As MEST is a benign tumor, preoperative diagnosis is crucial for avoiding overtreatment.

Renal angiomyoadenomatous tumour

Renal angiomyoadenomatous tumour is a newly described rare neoplasm. This tumour is characterised microscopically by admixture of three components- epithelial cells arranged in tubules and nests, angiomyomatous stroma and capillary sized interconnecting vascular channels in close association with the epithelial cell clusters. Microscopically it has wide range of differential diagnoses which include mixed epithelial and stromal tumour of kidney, angiomyolipoma and clear cell renal cell carcinoma with angiomyolipomatous/angiomyoadenomatous areas. Renal angiomyoadenomatous tumour should be differentiated from these tumours. Till now, only 10 cases have been reported in English medical literature. Here, we are reporting a case of renal angiomyoadenomatous tumour in a 29 year- old female patient who presented with hematuria and low backache and describing its main features so as to differentiate this entity from other renal tumours. To the best of our knowledge, this is the first case to be reported from India.

Pediatric Cystic Nephroma Is Morphologically, Immunohistochemically, and Genetically Distinct From Adult Cystic Nephroma

The term cystic nephroma has traditionally been used to refer to 2 neoplasms, a lesion in adults that is now thought to be part of the spectrum of mixed epithelial stromal tumor (MEST) and a pediatric lesion that has been associated with mutations in the DICER1 gene. A direct detailed morphologic, immunohistochemical, and genetic comparison of these 2 lesions has not been performed. In this study, we compare the morphologic features, immunoreactivity for estrogen receptor and inhibin, and DICER1 genetic status of 12 adult cystic nephroma/MEST (median age 50.5 y, all females) and 7 pediatric cystic nephroma (median age 1.3 y, male:female=6:1). Both lesions (11 of 12 adult cases, 6 of 7 pediatric cases) frequently demonstrated subepithelial accentuation of stromal cellularity, though the increased cellularity frequently included inflammatory cells in the pediatric cases. All adult and pediatric cases labeled for estrogen receptor; however, whereas most (83%) of adult cases labeled for inhibin at least focally, no pediatric case labeled for inhibin. Most adult cases (58%) demonstrated wavy, ropy collagen in association with cellular stroma, whereas this was not found in pediatric cases. 86% of pediatric cases demonstrated DICER1 mutations, whereas only 1 of 10 adult cases demonstrated a DICER1 mutation. In summary, although cellular stroma and estrogen receptor immunoreactivity are commonly present in both adult and pediatric cystic nephroma, ropy collagen and inhibin immunoreactivity are far more common in adult cystic nephroma/MEST, whereas DICER1 mutations are far more prevalent in pediatric cystic nephroma. These results support the current World Health Organization Classification's separation of adult and pediatric cystic nephromas as distinct entities.

Mixed Epithelial and Stromal Tumor of the Kidney: A Clinicopathologic Study of 53 Cases

Mixed epithelial and stromal tumor of the kidney is an uncommon complex neoplasm, and previous studies have included only a modest number of cases and have left gaps in our understanding of its morphology. We analyzed 53 tumors (46 F, median age: 49 y), collecting data on gross, histologic, and immunohistochemical features. The most common gross appearance was solid and cystic (47%). Hypocellular fibrous and cellular spindle cell stroma were the most common stromal types, followed by smooth muscle differentiation, edematous stroma, and adipose tissue. Hypocellular fibrous stroma and adipose tissue were more common in larger tumors (P=0.003 and 0.04, respectively) and cellular spindle cell stroma in smaller tumors (P=0.0009). Combinations of diverse stromal elements were common: roughly 50% of tumors contained >4 types of stroma. With regard to epithelium, tiny crowded and branching glands were present in 60% of tumors. Round glands lined by tall cuboidal epithelium, reminiscent of thyroid follicles, spatulate papillae reminiscent of phyllodes tumor, glands reminiscent of nephrogenic adenoma, and complex papillae were also frequently found. Combinations of diverse epithelial elements were common: 64% of tumors contained >4 types of epithelium. All of the tumors except 1 were positive for smooth muscle actin in the stroma. Desmin and caldesmon expression were more variable. Stains for progesterone and estrogen receptors showed positivity in the stromal component in 85% and 73% of tumors, respectively. CD10 and CD34 immunolabeling were restricted to pericystic spindle cells. No tumor expressed inhibin. In summary, this study demonstrates a strong tendency for mixed epithelial and stromal tumors to contain multiple types of stroma and epithelium and comprehensively analyzes the immunohistochemical profile.

Malignant Mixed Epithelial and Stromal Tumor of the Kidney With 2 Simultaneous Renal Carcinomas in a Male Patient: Case Report and Review of the Literature

The majority of mixed epithelial and stromal tumors (MEST) of the kidney are benign entities found in female patients. Malignant MEST of the kidney is an extremely rare entity that often behaves clinically similar to an undifferentiated sarcoma. We report a case of a malignant MEST with synchronous papillary and clear cell renal cell carcinomas (RCCs) in a 61-year-old Caucasian man who presented with an incidental finding of a left renal mass on workup for back pain. The patient underwent a left radical nephrectomy, with histopathology confirming a malignant MEST, intimately associated papillary RCC, and separate adjacent focus of clear cell RCC.

Angiomyolipoma With Epithelial Cysts

Angiomyolipoma with epithelial cysts is a rare mesenchymal tumor of the kidney that enters in the differential diagnosis of adult cystic renal neoplasms. These tumors demonstrate a slight female predominance and can present either incidentally or with symptoms, commonly flank pain and hematuria. Unlike conventional angiomyolipoma, this variant is characterized grossly by both solid and cystic areas, and histologically by the presence of single or multiple cysts lined by epithelial cells, a subepithelial "cambium-like" layer of small stromal cells with a prominent capillary vasculature, and a thick exterior wall composed of poorly formed fascicles of smooth muscle and thick-walled dysplastic blood vessels. Tumors show a distinct immunohistochemical profile and are often reactive for melanocytic markers (HMB-45 and Melan-A), as well as estrogen receptor and progesterone receptor. These tumors have an indolent clinical course, with no reports of progression or metastasis in reported cases thus far.

Benign mixed epithelial and stromal tumor of the kidney with inferior vena cava tumor thrombus: A rare case report and review of literature

Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare renal tumor composed of epithelial and stromal cells. In this study, we report a rare case of MESTK, which was pathologically benign but complicated with renal vein and inferior vena cava tumor thrombus. The 50-year-old female patient was admitted to hospital for a mass on the left kidney. Computed tomography showed a 32 mm×18 mm mass with slight delayed enhancement in the left renal sinus, and neoplastic thrombus was detected in left renal vein and inferior vena cava. A preoperative diagnosis of renal leiomyoma was made by needle biopsy and a laparoscopic radical nephrectomy with thrombectomy was performed. Histologically, the tumor and thrombus were composed of proliferative spindle cells and a small amount of tubular structures. Both kinds of the cells were well differentiated with no atypia or mitosis of nuclei. Immunohistochemical staining showed positive for CK, Ki-67 in the tubular cells and desmin, actin, estrogen receptors, progesterone receptors in the spindle cells. Finally, the diagnosis of MESTK was established. No recurrence or metastasis was found in the patient with a followed-up period of 12 months after the surgery. Due to the difficulty in diagnosis of MESTK, documentation with more cases of MESTK is needed to further understand its pathogenesis, biological behavior, preoperative diagnosis and optimal management of patient treatment.

Pathology of Pancreatic Cancer Precursor Lesions

To better understand pancreatic ductal adenocarcinoma (PDAC) and improve its prognosis, it is essential to understand its origins. This article describes the pathology of the 3 well-established pancreatic cancer precursor lesions: pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm. Each of these precursor lesions has unique clinical findings, gross and microscopic features, and molecular aberrations. This article focuses on histopathologic diagnostic criteria and reporting guidelines. The genetics of these lesions are briefly discussed. Early detection and adequate treatment of pancreatic cancer precursor lesions has the potential to prevent pancreatic cancer and improve the prognosis of PDAC.

Diagnosis of Renal Angiomyolipomas: Classic, Fat-Poor, and Epithelioid Types

With the increasing discovery of small renal masses with cross-sectional imaging, there has been the concomitant rise in their treatment. With the intent of early curative surgery for a presumed renal cell carcinoma, many renal masses are being resected at surgery without a confirmed diagnosis. Many of them are benign, and some are angiomyolipomas. The diagnosis of renal angiomyolipoma using imaging is, therefore, is as important as ever. Although most, if not all angiomyolipomas with abundant fat are diagnosed readily, some have too little fat to be detected with imaging. This article reviews the current classification, imaging pitfalls, and diagnosis of angiomyolipoma with an emphasis on the fat-poor types. Proper imaging technique, a thorough search for fat, and the appropriate use of percutanoeus biopsy are all needed to eliminate the unnecessary treatment of these benign neoplasms.

Morphological, immunohistochemical, and chromosomal analysis of multicystic chromophobe renal cell carcinoma, an architecturally unusual challenging variant

Chromophobe renal cell carcinoma (ChRCC) is typically composed of large leaf-like cells and smaller eosinophilic cells arranged in a solid-alveolar pattern. Eosinophilic, adenomatoid/pigmented, or neuroendocrine variants have also been described. We collected 10 cases of ChRCC with a distinct multicystic pattern out of 733 ChRCCs from our registry, and subsequently analyzed these by morphology, immunohistochemistry, and array comparative genomic hybridization. Of the 10 patients, 6 were males with an age range of 50-89 years (mean 68, median 69). Tumor size ranged between 1.2 and 20 cm (mean 5.32, median 3). Clinical follow-up was available for seven patients, ranging 1-19 years (mean 7.2, median 2.5). No aggressive behavior was documented. We observed two growth patterns, which were similar in all tumors: (1) variable-sized cysts, resembling multilocular cystic neoplasm of low malignant potential and (2) compressed cystic and tubular pattern with slit-like spaces. Raisinoid nuclei were consistently present while necrosis was absent in all cases. Half of the cases showed eosinophilic/oncocytic cytology, deposits of pigment (lipochrome) and microcalcifications. The other half was composed of pale or mixed cell populations. Immunostains for epithelial membrane antigen (EMA), CK7, OSCAR, CD117, parvalbumin, MIA, and Pax 8 were positive in all tumors while negative for vimentin, TFE3, CANH 9, HMB45, cathepsin K, and AMACR. Ki67 immunostain was positive in up to 1 % of neoplastic cells. Molecular genetic examination revealed multiple chromosomal losses in two fifths analyzable tumors, while three cases showed no chromosomal numerical aberrations. ChRCC are rarely arranged in a prominent multicystic pattern, which is probably an extreme form of the microcystic adenomatoid pigmented variant of ChRCC. The spectrum of tumors entering the differential diagnosis of ChRCC is quite different from that of conventional ChRCC. The immunophenotype of ChRCC is identical with that of conventional ChRCC. Chromosomal numerical aberration pattern was variable; no chromosomal numerical aberrations were found in three cases. All the cases in this series have shown an indolent and non-aggressive behavior.