Metanephric adenoma: A case report and literature review

@#This is a case of 27-year-old female who presented with a slow growing mass on the right flank. Computed tomography scan was done which revealed a cystic mass with septations and peripheral calcifications. Radical nephrectomy was performed on the patient. Histopathology and immunohistochemical staining were done which revealed features consistent with metanephric adenoma.

Chronology Of Nephrogenic Events In Staged Aborted Human Embryos And Fetuses

Introduction: The description given in various textbooks and literature on development of nephrons in humankidney doesn’t include details of chronology of nephrogenic events at various fetal ages. Though several studieswere reported the knowledge on development of kidney especially on the nephrogenesis are limited. The studiesemphasize the relationship between prenatal development of kidney and adult onset of renal diseases. Hence, anattempt was made in this study to obtain information by observing the serial sections of kidney of embryos andfoetuses of different gestational ages for better understanding of nephrogenic events.Material and methods: Thirty-five aborted embryos and dead fetuses of 5 weeks gestational age to full term wereutilized for this study. The specimens were subjected to routine tissue processing and haematoxylin and eosin(H&E) staining. 5 embryos of less than 8 weeks gestational age were processed as a whole and were seriallysectioned. The histological sections of 5 microns thickness were observed for the time of appearance of variousnephrogenic components and photographed.Results: Differentiating pronephric, mesonephric and metanephric components in different weeks i.e. 05 – 12, 13– 24, 25-36 were studied. In 06 – 12 weeks group a delay in the appearance of Pro and mesonephric, Meso andmetanephric ducts were observed that appeared during the 6th week. Differentiation of other components havenot completed by 6th week when compared with literature. In 13 – 24 weeks also there is delay in corticomedullary differentiation that was observed at 16 wks. at which time the morphologically recognizable Nephronswere also observed. Major part of development occurred between 16-28 weeks instead of 16-24weeks as statedin the literature. Ampulla division continued beyond 24 weeks. Increased number of mature nephrons wereobserved between 24-28 weeks instead of 16-20 wks., nephron arcades were observed during 24-28 weeksinstead of 14-22weeks.Conclusion: Detailed findings of this study could aid the embryologists, neonatologists and nephrologists tounderstand the chronology of nephrogenic events and related consequences of developmental abnormalities.

MSCT diagnosis of metanephric adenoma / 实用放射学杂志

Objective To investigate the performance of MSCT in the diagnosis of metanephric adenoma.Methods The imaging data of 5 cases of metanephric adenoma confirmed by operation and pathology in our hospital were collected and analyzed retrospectively.The location, size, shape, density and enhancement of the lesion were further retrospectively analyzed.Results In the incorporated 5 cases of metanephric adenoma, the male to female ratio of cases was 1:4, all were unilateral, including 2 cases of the right kidney,3 cases of the left kidney,2 cases were located in the upper pole, 2 cases in the polar region, 1 case in the lower pole of the kidney.Maximum diameter of the metanephric adenoma ranged from 2.9 cm to 8.4 cm, with an average value of 4.8 cm.The shape of metanephric adenoma was classified into: round (3 cases) and oval (2 cases).On plain scanning slightly lower density was found in 2 cases, equidensity in 2 cases and slightly higher density in 1 case.Furthermore,1 case had small punctatel calcification in the edge of the lesion,1 case with renal papillary carcinoma.4 cases underwent plain and enhanced scanning,and 1 case plain scanning,in which slight density increase after intravenous enhancement was showed in 3 cases,moderate enhancement in 1 case,more uniform enhancement in 3 cases,uneven enhancement in 1 case,delayed enhancement in 4 cases.Conclusion The characteristic MSCT features of metanephric adenoma have a certain specificity.Preoperative correct understanding is helpful to guide the operation scheme.

Progress in genetics of vesicoureteral reflux / 国际儿科学杂志

Vesicoureteral reflux,a most common congenital anomaly of the kidney and urinary tract,is associated with the malformation of ureterovesical junction. It does not cause any specific symptoms or signs un-less it is part of a syndrome or complicated by urinary tract infection. The exact cause is not clear,and genes or environmental factors may result in vesicoureteral reflux. The prevalence of siblings and offspring of reflux pa-tients are higher than normal control groups,so the genetic screening is necessary. This article will review the ge-netics of vesicoureteral reflux and possible interactions.

Molecular regulation of kidney development / 대한해부학회지

Genetically engineered mice have provided much information about gene function in the field of developmental biology. Recently, conditional gene targeting using the Cre/loxP system has been developed to control the cell type and timing of the target gene expression. The increase in number of kidney-specific Cre mice allows for the analysis of phenotypes that cannot be addressed by conventional gene targeting. The mammalian kidney is a vital organ that plays a critical homeostatic role in the regulation of body fluid composition and excretion of waste products. The interactions between epithelial and mesenchymal cells are very critical events in the field of developmental biology, especially renal development. Kidney development is a complex process, requiring inductive interactions between epithelial and mesenchymal cells that eventually lead to the growth and differentiation of multiple highly specialized stromal, vascular, and epithelial cell types. Through the use of genetically engineered mouse models, the molecular bases for many of the events in the developing kidney have been identified. Defective morphogenesis may result in clinical phenotypes that range from complete renal agenesis to diseases such as hypertension that exist in the setting of grossly normal kidneys. In this review, we focus on the growth and transcription factors that define kidney progenitor cell populations, initiate ureteric bud branching, induce nephron formation within the metanephric mesenchyme, and differentiate stromal and vascular progenitors in the metanephric mesenchyme.

Diagnosis and treatment of metanephric adenoma / 中华泌尿外科杂志

Objective To explore the clinical and histopathological features of metanephric adenoma (MA). MethodsClinical and pathological data of 10 cases of MA were analyzed retrospectively.There were 4 males and 6 females,aged from 33 to 65 years,with an average of 45 years.2 patients had flank pain,4 patients had gross hematuria,and 4 patients were found by physical examination.The average diameter of tumor was 4.5 cm (2.5 - 8.0 cm).All patients were diagnosed as renal tumor by CT scan.9 patients underwent radical nephrectomy and 1 patient underwent partial nephrectomy. Results Pathological examination found that the tumors are composed of densely packed small uniform cells with regular nuclei that formed a tubular or adenoid pattern.Mitotic figures were absent or rare.4 patients were diagnosed as MA,2 cases were diagnosed as low-grade malignant MA,and 4 cases were diagnosed as MA with malignant component (2 cases of adenocarcinoma,1 case of chromophobe cell carcinoma,and 1 case of well differentiated papillary adenocarcinoma),7 cases were followed up for 22 months ( 10 to 34 months) without recurrence or metastasis. Conclusions MA is very rare benign renal tumor originating from epithelium,and a few are malignant,and some may contain malignant ingredients.Nephron-sparing surgery and radical nephrectomy are eligible for the treatment of MA.Considering the uncertainty of the biological behavior and cellular origin of MA,a long-term follow-up is necessary.

Expression of Robo2 gene during the renal development in mice / 解放军医学杂志

Objective To observe the expression of Robo2 gene, and explore its role during the renal development of mice. Methods Real-time quantitative RT-PCR was used to semi-quantitatively measure the expression level of Robo2 mRNA in the developing murine kidney at fetal age of 12.5, 13.5, 14.5, 15.5, 16.5 and 17.5 days, and also 1 day, 1 week, 5 weeks after birth. Immunofluorescence staining was used to examine the expression location of Robo2 protein at different stages of embryonic and postnatal kidney. Results Real-time quantitative RT-PCR analysis revealed that Robo2 was highly expressed in embryonic kidney at fetal age of 12.5, 13.5 and 14.5 days, while the expression level declined quickly thereafter and maintained at very low level after birth. Immunofluorescence staining showed that the expression of Robo2 protein could be primarily detected in metanephric mesenchyme of the developing kidney, but not in the ureteric bud. With the development of embryonic kidney, Robo2 protein was expressed in cell membrane of metanephric mesenchyme, condensed cap mesenchyme surrounding the tip of the ureteric bud, comma-shaped body, S-shaped body and renal capsule, finally expressed in the podocytes. Besides, Robo2 protein was also weakly expressed in part of the proximal tubular epithelial cells. Absence of Robo2 gene resulted in abnormal development of nephron, and broadening of some renal tubules and collecting ducts. Conclusion Robo2 plays an important role in the nephron development in mice by regulating the interaction of metanephric mesenchyme and ureteric bud.

Anomalías congénitas del sistema renal: agenesia renal izquierda asociada a variante arteriovenosa renal derecha y vena cava inferior / Congenital anomalies of the renal system: left renal agenesis associated with right renal arteriovenous variant and inferior vena cava

Este trabajo describe la variante anatómica en un caso incidental de disección en la Escuela de Medicina de la Universidad de Costa Rica, el cual presenta agenesia renal izquierda con variante arteriovenosa renal derecha que consta de cinco arterias renales y dos venas renales, asociado a la variante anatómica del origen de la vena cava inferior ya que es superior a la arteria mesentérica inferior.

This work describes the anatomic variation from an incidental case of dissection founded at Costa Rica’s University School of Medicine, which presents left renal agenesia with a right arteriovenous variant which consists of five renal arteries and two renal veins, related to the anatomic variant from the inferior cava vein, this variation its superior to the inferior mesenteric arterie.

Metanephric stromal tumor: A novel pediatric renal neoplasm.

Metanephric stromal tumor of kidney is a novel pediatric benign stromal specific renal neoplasm. A few cases have been reported in adults also. This tumor is usually centered in the renal medulla with a characteristic microscopic appearance which differentiates this lesion from congenital mesoblastic nephroma and clear cell sarcoma of the kidney. In most cases complete excision alone is curative. The differentiation of metanephric stromal tumor from clear cell sarcoma of the kidney will spare the child from the ill effects of adjuvant chemotherapy. In this communication we describe the gross and microscopic features of metanephric stromal tumor in a one-month-old child with good prognosis.

A Case of Horseshoe Kidney / 체질인류학회지

During cadaver dissection at Chungnam National University in year 2001, we found a case of horseshoe kidney. The characteristic findings of this kidney were as follows; 1. Horseshoe kidney was located at the level of 12th thoracic vertebra and 4th lumbar vertebra, and its isthmus was located at the level of 3rd lumbar vertebra, just below inferior mesenteric artery. The upper pole of the right kidney was 11 mm higherthan that of left kidney. 2. Both renal arteries originated normally from the abdominal aorta below superior mesenteric artery and divided into 2 branches at the front of the renal hilum. The lower branches entered normally into the renal hilum respectively, but, 2 upper branches of right renal artery and 3 upper branches of left renal artery entered into the upper segment of both kidneys respectively. 3. The 2 accessory renal arteries were found. One was the branch of the median sacral artery, which asended anterior to the bifurcation of abdominal aorta and divided 2 branches, of which larger right branch entered inferior pole of right kidney and smaller left branch entered into the isthmus. The other was originated from abdominal aorta 1/3 distance from the origin of inferior mesenteric artery to the bifurcation of abdominal aorta, and entered into the posteroinferior part of left kidney. 4. There were additional 2~3 minor calyces in the lower part of the both kidneys in frontal section, which formed a major calyx draining into the renal pelvis. Parenchymal tissues of both kidneys were continuous through isthmus. In frontal section, renal pyramids were twice in number, and arranged into 2 groups at the upper and lower parts of the both kidneys. Especially, one renal pyramid laid transversely in the isthmus and the renal papilla of it opened into the minor calys of left kidney. It is thought that this horseshoe kidney might be resulted from the elongation of a ureteric bud, which induced new broad -field nephron within the metanephric blastema, and formed a group of additional renal pyramids. The additional renal pyramids formed slight later than normal period, and the separation of both kidneys should be failed and resulted horseshoe kidney. During ascent of kidney, the inferior mesenteric artery interrupted upward migration. It can be concluded that the error of reciprocal induction between ureteric bud and metanephric mesenchyme may be an important mechanism of horseshoe kidney formation.

Metanephric Adenoma of the Kidney

Metanephric adenoma is a rare renal epithelial tumor. Its light microscopic features are very characteristic, and immunohistochemical and electron microscopic studies are not critical to the diagnosis. The literature indicate that, to date, the tumor has behaved in a benign fashion, and predominantly but not exclusively occurred in middle-aged women. It occurs in a wide range up to 11 cm and is usually an incidental finding but may be symptomatic with hematuria or flank pain. Recently, we have experienced a case of renal tumor showing distinctive adenomatous features, which is incidentally found in a 52-year-old female. This tumor is confined to the renal cortex and is well-circumscribed with a characteristic uniform and orderly proliferation of compact well-differentiated small tubules lined by bland oval cells with a very low level of mitotic activity. The term metanephric adenoma is appropriate for this tumor because it accurately describes its bland proliferation of tubules and reflects the embryonic architectural and cytological appearance of this proliferation. The pattern of the tumor, with its occasional papillary glomeruloid- like bodies and foci of elongated tubules, is reminiscent of the fetal metanephric kidney.