Metanephric adenoma of the kidney: clinical and radiological study of nine cases

Metanephric adenoma in children: A case report and literature review

Metanephric adenoma (MA) is a rare type of benign renal epithelial tumor that can develop at any age. Nonetheless, MA is extremely rare in children and only a few cases have been reported to date. The present study aimed to report the case of a 5-year-old female found to have a mass in the right kidney during a routine pre-enrollment physical examination. Computed tomography (CT) images revealed multiple high-density calcifications in the mass, and contrast-enhanced CT and magnetic resonance imaging demonstrated that the mass was significantly enhanced in the cortical phase and decreased in the medullary phase. Based on these findings, the mass was initially diagnosed as angiomyolipoma before surgery; however, postoperative pathology confirmed the mass to be a MA. MAs are typically a type of soft tissue mass with relatively uniform density or signal, showing delayed enhancement in contrast-enhanced scanning. However, the mass found in the present study presented diffused high-density calcification, which was obvious in the early phase of contrast-enhanced scanning but weakened in the delayed enhancement phase. In conclusion, the present case study demonstrated that MA should be considered as one of the imaging differential diagnoses of fat-poor angiomyolipoma, renal carcinoma and oncocytoma.

Pediatric metanephric adenoma with Fanconi-Bickel syndrome: a case report and review of literature

Background

Metanephric adenoma (MA) is a rare benign renal tumor that resembles renal cell carcinoma and Wilms’ tumor in radiological as well as pathological appearance. It can present at any age or gender, and it is extremely rare in the pediatric age group with less than 50 reported cases. Fanconi–Bickel syndrome (FBS) is a rare autosomal recessive disorder of carbohydrate metabolism. Herein, we report a rare incidence of MA in a boy with a genetically confirmed FBS who underwent a nephron-sparing surgery.

Case presentation

A 21-month-old boy was referred to the pediatric urology clinic for further evaluation of an incidentally discovered left renal mass. His laboratory investigations showed normal renal function, hypophosphatemia, high blood glucose level, markedly elevated serum alkaline phosphatase, and low serum vitamin D. Blood picture showed signs of polycythemia and urinalysis showed glucosuria and aminoaciduria. Genetic testing was positive for Fanconi–Bickel syndrome. Radiological investigations were carried out with abdominal ultrasound and computerized tomography (CT) with intravenous contrast documented a sharply marginated peripheral hypoechoic hypovascular homogeneously enhancing mass at the upper pole of the left kidney measuring 2.0 × 1.8 × 2.0 cm. The child was admitted and started on supportive treatment until his medical condition was stabilized, then underwent elective open left partial nephrectomy via a left upper transverse abdominal transperitoneal incision. The excised renal mass was sent for histopathological assessment and was found to be a tumor composed of tightly packed tubules with no mitotic figures or necrosis and scanty cytoplasm consistent with MA. After good hydration and tumor resection, his polycythemia gradually improved. The patient was discharged home in a good condition with his proper replacement therapies. His follow-up abdominal ultrasound after 12 months showed no signs of recurrence.

Conclusions

Metanephric adenoma is extremely rare in the pediatric age group, especially in those who have a FBS. The only way to diagnose and treat this tumor is by surgical resection as most patients are asymptomatic. A nephron-sparing surgery is better for this age group in which the future renal function is considered.

Chemotherapy Combined With Surgery in a Case With Metanephric Adenoma

BACKGROUND

Metanephric adenoma is an extremely rare renal neoplasm, especially in pediatrics. Chemotherapy combined with surgery in metanephric adenoma has not been reported.

METHODS

We describe a case of metanephric adenoma in a child less than 2 years old, which were treated by chemotherapy combined with surgery.

RESULTS

Nephron sparing surgery was performed after regular chemotherapy, and the pathological result was metanephric adenoma.

CONCLUSION

Pediatric metanephric adenoma is extremely rare; the clinical manifestations and imaging examinations lack specificity. Nephron sparing surgery is recommended as the preferred treatment for metanephric adenoma. Long-term follow-up and more in-depth molecular genetic research are still needed to determine the benign or malignant of metanephric adenoma and whether chemotherapy drugs have an effect on it.

Metanephric adenoma: association between the imaging features of contrast-enhanced ultrasound and clinicopathological characteristics

Background

This study aimed to improve the understanding of metanephric adenoma (MA) by retrospective analysis of contrast-enhanced ultrasound (CEUS) findings and clinicopathological characteristics of MAs.

Methods

Gray-scale ultrasound (US) and CEUS findings of 7 adult MA patients, confirmed by postoperative pathology, were summarized via collection of clinicopathological and ultrasonographic imaging data, including tumor location, size, echo intensity, color flow, presence or absence of calcification, and liquefactive necrosis, contrast-enhanced pattern, enhancement characteristics, and contrast wash-out compared with adjacent parenchyma, and the presence or absence of a pseudocapsule. Histopathological analyses, including hematoxylin and eosin (HE) and immunohistochemical (IHC) staining, were conducted with the EnVision method.

Results

All 7 participants were female, aged 29-73 years (mean age, 54 years), with flank pain (3/7). All tumors were solid (7/7) with sizes of 2.0-5.0 cm (mean diameter, 3.07 cm), including 4 in the left kidney, 3 in the right kidney, 2 in the renal pelvis, and 5 in the renal parenchyma. On the gray-scale US, MA was shown as hypoechoic (4/7), slightly hyperechoic (2/7), isoechoic (1/7), and with a defined border. The morphology was regular and rounded (7/7), internal echogenicity was homogeneous (5/7), and no calcification was seen (7/7). The CEUS showed clear boundaries (7/7), homogeneous isodensity (5/7), with calcification (0/7), necrosis (2/11), heterogeneous hyperattenuation (2/7), pseudocapsule (2/7), and medullary phase fast wash-out (7/7). The surgical methods were radical nephrectomy (4/7) and partial nephrectomy (3/7). The duration of follow-up period for all participants was 3-74 months, and no local or distant recurrences were found. The IHC staining showed that most tumor cells were positive for WT1, cytokeratins AE1/AE3, vimentin, and CD57, and exhibited focal positivity for CK7, while negative for CD10, AMACR, and CK720. The proliferative index (Ki-67) was 2-3%.

Conclusions

On gray-scale US, MA appears as a solid nodule with a well-defined boundary, regular morphology, and homogeneous echogenicity; CEUS shows slow progression and slightly lower homogeneous enhancement and fast wash-out in the medullary phase. These findings may provide insight into the progression of MA and aid in the development of diagnostic and therapeutic strategies.

[Metanephric adenoma, a benign variant of Wilms' tumour: case report of an extremely rare kidney tumour and literature survey]

Rare benign tumours of the kidney comprise a group of very different histogenetic entities. We report a case of a 53-year-old woman who underwent laparoscopic nephrectomy because of a renal mass. The diagnosis of a rare and benign metanephric adenoma was confirmed by histopathology. With less than 200 documented cases, the metanephric adenoma described here is a rarity in everyday urological practice and cannot be distinguished from a malignant tumour of the kidney by clinical examination and/or imaging without histological assessment.

Experience of diagnosis and management of metanephric adenoma: retrospectively analysis of 10 cases and a literature review

Background

Metanephric adenoma (MA) is a rare benign tumor with only several hundred cases reported worldwide to date. Herein, we retrospectively summarized the experience of diagnosis and management of ten MA cases.

Methods

A total of ten MA patients were included in this study definitely diagnosed by postoperative immunohistochemistry at the First Affiliated Hospital of Nanjing Medical University from January 2010 to January 2019. Clinical characteristics, image features, therapeutic procedures, histological diagnosis and outcomes of them were retrospectively analyzed.

Results

Characteristics of the patient population were nine females and one male with age of 36.8±17.5 years. The mean tumor size was 33.6 mm (range from 35.0 to 70.0 mm). Among them, nine cases were asymptomatic and one case showed acute flank pain. All ten cases underwent plain and enhanced computed tomography (CT) scan. Laparoscopic partial nephrectomy (LPN) was performed in seven cases and laparoscopic radical nephrectomy (LRN) was applied in the other three cases. Postoperative routine pathology results confirmed that seven cases were MA. However, two patients were misdiagnosed with papillary renal cell carcinoma (PRCC), and another was misdiagnosed with Wilms’ tumor. Further immunohistochemistry eventually confirmed all these ten cases as MA. During a mean follow-up of 58.3 month, all ten patients were alive with no local recurrences nor metastases.

Conclusions

In summary, MA is a rare benign tumor with no distinct clinical symptoms. The definite diagnosis depends on the postoperative pathological findings. Fortunately, due to its non-malignant nature, patients always have a good prognosis.

Pediatric Renal Neoplasms:: MR Imaging-Based Practical Diagnostic Approach

Pediatric renal tumors may be malignant or benign. Wilms tumor, the most common malignant pediatric renal tumor, arises sporadically or with various syndromes. Renal cell carcinoma typically presents in older children. Renal clear cell sarcoma and rhabdoid tumor are typically less common, more aggressive, and present in younger children. Benign renal tumors include mesoblastic nephroma, multilocular cystic renal tumor, angiomyolipoma, and metanephric adenoma. Lymphoma and leukemia may secondarily involve the kidney. Although there is overlap in the imaging appearance of several pediatric renal tumors, magnetic resonance characteristics and clinical data narrow the differential diagnosis and suggest a specific diagnosis. This article reviews current MR techniques, as well as the common MR imaging characteristics of malignant and benign pediatric renal neoplasms.

Imaging features of metanephric adenoma and their pathological correlation

AIM

To analyse the imaging features of metanephric adenoma (MA) and their pathological correlation.

MATERIALS AND METHODS

The imaging findings in 11 patients with MA were studied retrospectively. Ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) findings were studied in seven, 11, and six patients, respectively. The enhancement pattern, attenuation, lesion location, size, cystic or solid appearance, capsule sign, and presence of calcifications were evaluated.

RESULTS

On ultrasonography, MA presented as hypoechoic (4/7), slightly hyperechoic (1/7), isoechoic (2/7), and with a clear boundary. Unenhanced CT showed unclear boundaries (11/11), homogeneous isodensity (8/11), with calcification (1/11), necrosis (1/11), and heterogeneous hyperattenuation (1/11). Mean CT attenuation values on unenhanced and enhanced CT (cortical phase, corticomedullary phase, and excretory phase) were 38.87±6.66, 55.71±17.74, 67.77±16.86, and 65.62±15.99 HU, respectively. The degree of enhancement of the lesions in each phase was statistically significantly lower than that of the surrounding normal renal parenchyma (p=0.00). The pattern of enhancement of the solid component was slight and gradual enhancement (9/11). The tumour was located entirely within the renal medulla in nine cases, and two cases demonstrated an exophytic pattern. All tumours showed a clear boundary on enhanced CT, but capsules were not found. The mean greatest tumour diameter was 3.5 cm. MA showed markedly hyperintense on the diffusion-weighted MRI sequence (DWI) and delayed enhancement of the tumour capsule on enhanced MRI.

CONCLUSIONS

Imaging features of MA are usually solid and hypovascular, and show prolonged, and homogeneous mild enhancement that is less than that of the surrounding normal renal parenchyma in all phases. MA is markedly hyperintense on DWI.

Novel clinicopathological and molecular characterization of metanephric adenoma: a study of 28 cases

Background

Metanephric adenoma is a rare, benign renal neoplasm with occasional misdiagnosis. However, its molecular characterization is not fully understood.

Methods

In this study, we use the hybrid capture-based Next-Generation Sequencing to sequence a panel of 295 well-established oncogene or tumor suppressor genes in 28 cases of MA patients in China. Novel clinicopathological markers associated with the mitogen-activated protein kinase (MAPK) pathway in metanephric adenoma were detected by immunohistochemistry.

Results

It was found that except for BRAF (22/28) mutations (c.1799 T > A, p.V600E), NF1 (6/28), NOTCH1 (5/28), SPEN (5/28), AKT2 (4/28), APC (4/28), ATRX (3/28), and ETV4 (3/28) mutations could also be detected. Meanwhile, a novel and rare gene fusion of STARD9-BRAF, CUX1-BRAF, and LOC100507389-BRAF was detected in one MA patient. In addition, although MEK phosphorylation was normally activated, the phosphorylation level of ERK was low in metanephric adenoma cases. Highly expressed p16 and DUSP6 may have contributed to these results, which maintained MA as a benign renal tumor.

Conclusions

This study provides novel molecular and pathological markers for metanephric adenoma, which could improve its diagnosis and increase the understanding of its pathologic mechanism.

Electronic supplementary material

The online version of this article (10.1186/s13000-018-0732-x) contains supplementary material, which is available to authorized users.

An "accidental" discovery: Incidentally found metanephric adenofibroma in a 5-year-old male trauma patient

Metanephric adenofibroma is a rare pediatric renal tumor, which should be considered in cases of solid renal lesions that mimic Wilms tumor on both imaging and histology. We present a case of an incidentally found left renal lesion on a trauma computed tomography scan in a 5-year-old male patient. The patient underwent total nephrectomy, and the diagnosis of metanephric adenofibroma was made on histology. Radiologists should consider this entity in the differential for an incidentally found solitary renal mass in a pediatric patient. Prompting the pathologic diagnosis of this entity can spare patients from unnecessary chemotherapy and allow for nephron-sparing surgery.

Renal Tumors of Childhood: Radiologic-Pathologic Correlation Part 2. The 2nd Decade: From the Radiologic Pathology Archives

Malignant renal tumors account for 7% of childhood cancers, and Wilms tumors are by far the most common-but not in older children and adolescents. Among individuals in the latter half of their 2nd decade of life, renal cell carcinoma (RCC) is more common than Wilms tumor. The histopathologic spectrum of RCCs in children differs from that in adults. The most common subtype of RCC in children and adolescents is Xp11.2 translocation RCC, which is distinguished by hyperattenuation at nonenhanced computed tomography, a defined capsule, and associated retroperitoneal lymphadenopathy. Papillary RCC is the second most common histologic subtype. It enhances less intensely compared with the adjacent renal parenchyma and has a propensity for calcification. Clear cell RCC is seen in patients with von Hippel-Lindau disease and is distinguished by its relatively hypervascular nature. Medullary carcinoma affects adolescents with the sickle cell trait and is characterized by an infiltrative growth pattern and extensive metastasis at presentation. Angiomyolipoma is seen in children with tuberous sclerosis complex and is often multifocal and hypervascular, with macroscopic fat. Metanephric tumors are central, circumscribed, and typically calcified. Lymphoma usually manifests as multifocal masses, but it may involve a solitary mass or infiltrative pattern. Extensive adenopathy and involvement of the gastrointestinal tract or other organs also may be seen. Primitive neuroectodermal tumor is an aggressive neoplasm that is typically quite large at diagnosis. Knowledge of the clinical, biologic, and histopathologic features of renal tumors in older children and adolescents and their effects on the imaging appearance can help the radiologist offer a useful preoperative differential diagnosis.

The findings of CT and MRI in patients with metanephric adenoma

Background

Metanephric adenoma (MA) is a benign renal tumor that is difficult to distinguish from a malignant tumor via traditional radiography. The diagnosis of MA is often dependent on postsurgical histopathological examination. In the present report, the imaging features of MA on computer tomography (CT) and magnetic resonance imaging (MRI) were retrospectively evaluated.

Methods

Eight MA patients, 17–67 years of age, were pathologically confirmed and recruited between April 2009 and November 2014. Four of the eight patients were female. All patients underwent CT scanning, and one patient underwent MRI scanning. Three patients underwent CTA of the renal arteries. All patients underwent resection surgery (radical nephrectomy in five and nephron-sparing surgery in three patients).

Results

The average tumor size was 44.0 ± 23.6 mm. The lesions in 87.5 % cases were located both in the renal cortex and medulla and exhibited exophytic growth. Plain CT showed that MA tumors were solid, and the average CT value was 37.9 ± 6.7 HU. Dynamic contrast-enhanced CT revealed that enhanced degrees of MA tumors in the renal cortex, renal parenchymal, and pelvic phase were all lower than that of normal renal parenchyma. A slight enhancement in the renal cortex phase and an even higher enhancement in the renal parenchymal phase were observed in seven of the cases. Progressive enhancement in the pelvic phase was found in five cases and a slight decreased enhancement in the pelvic phase in two cases. MRI revealed that MA tumor was isointense on T1WI and isointense on T2WI with some slightly hyperintense areas in the center. CTA of the renal arteries revealed the nutrient artery in one patient and no nutrient artery in two. Immunohistochemical experiments demonstrated that most tumor cells were positive for vimentin, CK, and EMA.

Conclusions

MA is a rare benign renal neoplasm. Detailed knowledge of the CT and MRI characteristics of MA plays an important role in MA diagnosis and treatment.

Metanephric adenoma with diffuse calcifications: A case report

Metanephric adenoma is a rare and benign renal neoplasm originating in the epithelial cells of the kidney. The tumor has a benign course and a characteristic histopathological appearance, typically exhibiting a solid and poorly-demarcated margin with rare cystic components or calcifications. However, it is often difficult to distinguish metanephric adenoma from malignant neoplasms prior to surgical resection. To the best of our knowledge, only one case of metastasis to the lymph nodes has been described in the literature thus far. The present study retrospectively analyzed one case of surgically and pathologically-confirmed atypical metanephric adenoma. Clinical and pathological analysis, as well as computed tomography scans, revealed a mass with a clearly defined margin and diffuse calcifications. The mass was subsequently resected and the patient recovered well following the procedure.

A metanephric adenoma of the kidney associated with polycythemia: A case report

Metanephric adenoma (MA) of the kidney is a rare and frequently benign tumor with a favorable prognosis that is often diagnosed following surgical treatment. In the present study, a 54-year-old female patient presented with complaints of intermittent right-flank pain and anterior abdominal pain occurring over 2 years and sporadic gross hematuria occurring over 3 months. Ultrasonography and computerized tomography imaging revealed a neoplasm lesion localized in the right kidney. Successful open approach radical nephrectomy was performed and post-surgical histopathological examination verified the lesion as a MA of the kidney. Radical nephrectomy, cryoablation or radiofrequency may used to treat MA and a selective panel of immunostains, including WT1, EMA and AMACR, may be useful for diagnosis.

Adult metanephric adenoma presumed to be all benign? A clinical perspective

Background

In most documented literature, metanephric adenoma (MA) is described as a benign tumour. Nevertheless, the nature of MA remains unclear and the clinical criteria of different MA subtypes are not well established. In the present study, we investigated the clinicopathological characteristics of MA, especially those of the uncommon histological subtypes.

Methods

A cohort study was performed on 18 patients with pathologically proven MA in our institute from January 2004 to June 2014. The patients’ clinicopathological and radiological data were retrospectively analysed and evaluated with an emphasis on the corresponding subtypes.

Results

The patient population had a female: male ratio of 1:1 and mean age of 50 years (range, 18–66 years). The mean tumour size was 3.9 cm (range, 1.4–9.0 cm). There were no pathognomonic radiological features that posed a challenge for a preoperative diagnosis of MA. Fourteen patients underwent radical nephrectomy, and the other four underwent partial nephrectomy. Three histological subtypes were observed: classic MA (n = 10), malignant MA (n = 2), and composite MA with coexistence of different malignant components (n = 6). Despite the presence of atypical histological features and malignant components among the patients, only one patient developed distant metastasis (median postoperative follow-up, 56 months; range, 30–86 months).

Conclusions

MAs are a heterogeneous group of neoplasms with different biological characteristics. The correct identification of this entity and its subtypes would facilitate stratification of optimal management protocols and accurate assessment of the prognosis.

BRAF mutations in pediatric metanephric tumors

Metanephric neoplasms of the kidney are uncommon, and some cases are associated with papillary carcinoma. Most cases of metanephric adenoma occur in adults, with fewer than 25 cases reported in children, and metanephric adenofibroma is even less common. The few metanephric tumors studied at the genetic level have not shown the gains of chromosomes 7 and 17 commonly seen in renal cell carcinoma, suggesting that the carcinoma arising in this setting has a separate genetic origin from the adenoma. However, the assumption that this carcinoma has the same chromosome gains as sporadic renal cell carcinoma has never been validated. We studied 4 cases of metanephric tumors in children, including 1 metanephric adenofibroma with papillary carcinoma. The composite tumor was studied by single nucleotide polymorphism array and fluorescence in situ hybridization, with the adenoma and carcinoma components analyzed separately. No copy number alterations were detected in either component. A BRAF V600E mutation has been reported in most cases of metanephric adenoma in adults. We performed BRAF V600E immunostaining and sequencing in our 4 pediatric cases. Three cases had a BRAF V600E mutation including the composite tumor, with both the adenoma and carcinoma components showing the same mutation. This finding provides the first genetic evidence that these 2 tumors are biologically linked. Ten cases each of pediatric renal cell carcinoma and Wilms tumor were immunonegative. Thus, BRAF V600E immunostaining is a helpful marker for pediatric metanephric adenoma, and additional research is required on the possible role of this mutation in the development of renal carcinoma.

The clinical and CT imaging features of metanephric adenoma

BACKGROUND

Patients with metanephric adenoma have a good prognosis after undergoing total nephrectomy or local resection with kidney preservation. Accurate diagnosing is important for guiding clinical treatment. Only few previous case reports have been found focusing on the imaging findings of metanephric adenoma.

PURPOSE

To evaluate the multislice computed tomography (MSCT) imaging characteristics of metanephric adenoma.

MATERIAL AND METHODS

The imaging findings in eight patients with metanephric adenoma were studied retrospectively. MSCT was undertaken to investigate tumor location, size, attenuation, cystic or solid appearance, calcification, capsule sign, and enhancement pattern.

RESULTS

Tumors (mean diameter, 3.3 ± 1.0 cm) were solitary (8/8), solid (7/8) with cystic components (2/8), no calcifications (7/8), had a poorly-defined margin (8/8), were centered in the renal medulla (7/8), compressed the renal pelvis (3/8), and none had retroperitoneal lymph node metastasis. The attenuation of metanephric adenoma tumors was less or equal compared to the renal cortex or medulla on unenhanced CT (30.6 ± 2.6 vs. 36.3 ± 4.6 vs. 33.2 ± 3.9, P > 0.05), while tumor enhancement after administration of an contrast agent was lower than that of normal renal cortex and medulla during all phases (P < 0.05).

CONCLUSION

Metanephric adenoma tends to be a solitary, poorly defined margin, isodense or hypodense mass arising from the renal medulla with enhancement less than the cortex and medulla during all phases.

Metanephric adenoma: A report of two cases and review of the literature

Metanephric adenoma (MA) is a rare benign renal neoplasm of originating in the epithelial cells, which is often difficult to distinguish from malignant neoplasms preoperatively. In this study we present two cases of patients with MA with the aim to analyze the clinical manifestations, imaging, pathology, diagnosis and treatment of MA. Computed tomography (CT) of the first case revealed a solid well-demarcated tumor, 5.5 × 5.4 cm in diameter. Ultrasound examination of the second patient revealed a hypoechoic mass with solid aspect and irregular limits in the upper pole of the right kidney. CT confirmed the presence of a 4 cm expansive tumoral formation with intermediate attenuation and minimum venous contrast enhancement at that anatomic site. The two cases underwent surgery and the patients were free from recurrence after a follow-up period of 18 months to 2 years. We also present a supplementary review of previously published cases and related literature.

Pediatric metanephric adenoma: case report and review of the literature

Metanephric adenomas are rare benign renal neoplasms, uncommonly seen in the pediatric population. They are typically detected incidentally on imaging studies performed for unrelated clinical presentations. Preoperatively, the imaging appearance of this tumor overlaps with the appearance of more common and more aggressive renal neoplasms such as Wilms' tumor or renal cell carcinoma. We present a case of a pathologically proven metanephric adenoma, monitored preoperatively for approximately 5 years, prior to definitive nephrectomy. As the majority of solid renal masses are resected soon after they are detected, to the best of our knowledge, this case is the first to demonstrate the natural in vivo progression of a pathologically proven metanephric adenoma.

A case of a metanephric adenoma of the kidney surgically treated with robot-assisted laparoscopic partial nephrectomy

Metanephric adenomas are a rare neoplasm of the kidney with less than 200 cases reported. We report a case of a metanephric adenoma incidentally found on imaging in a 52-year-old Hispanic female and treated with robot-assisted laparoscopic partial nephrectomy. A brief review of the literature is also included.

Fine-needle aspiration of metanephric adenoma of the kidney with clinical, radiographic and histopathologic correlation: a review

Metanephric adenoma of the kidney is an uncommon benign epithelial neoplasm with only a small number of reports that describe its cytologic features. We describe two additional cases of metanephric adenoma diagnosed on fine-needle aspiration biopsy and review the available literature. Our cases showed similar cytology and were composed of cellular smears with numerous clusters of small, oval to round cells arranged in a microfollicular pattern and papillary configurations. The tumor cells had scant cytoplasm, fine chromatin and absent nucleoli. Psamomma bodies, nuclear atypia, cellular cpleomorphism, necrosis, and mitoses were absent. Because of the rarity of this tumor and the common cytologic features it shares with other lesions, including malignant tumors such as Wilms' tumor and papillary renal cell carcinoma, awareness of the cytologic features of metanephric adenoma may aid in avoiding a diagnosis of malignancy, especially preoperatively, and in guiding the proper management for the patients.

Renal angiomyoadenomatous tumour: Imaging features

Renal angiomyoadenomatous tumour is a rare, recently described neoplasm with a distinctive histological appearance. Although reported in the pathology literature, to our knowledge, no prior reports have described its imaging appearance. We describe the computed tomography and magnetic resonance imaging features of an incidentally detected renal angiomyoadenomatous tumour that appeared as a well-marginated, solid T2-hypointense enhancing mass, in a 50-year-old woman. It is indistinguishable from a variety of benign and malignant renal neoplasms.

Metanephric Adenoma of the Kidney: Study of Eight Patients and Review of the Literature

Background

Metanephric adenoma is a rare benign tumor of the kidney polycythemia is associated and it might be possible to suspect the diagnosis of this neoplasia.

Methods

From the beginning of 2000 till the end 2011, we identified eight male patients with methanephric adenoma in our hospital, only two of these were selected to surgery for this tumor; in the other six the finding occasionally at pathological anatomy other pathology of the kidney.

Results

All patients are in good clinical condition except two died for other diseases. The mean (range) dimension was about 2 cm.

Conclusion

The adenoma is a benign condition; suspect this adenomais recommended nephron sparing surgery.

A case of central metanephric adenoma successfully treated with laparoscopic nephron-sparing surgery

Metanephric adenoma is an extremely rare renal tumor and, even more infrequently, is centrally located. Herein we summarize a series of images concerning a central metanephric adenoma in a female adult successfully treated with laparoscopic nephron-sparing surgery. The patient presented with no symptoms but was found to have a lesion in the middle portion of the left renal parenchyma for 1 month prior. She underwent retroperitoneal laparoscopic nephron-sparing surgery with total resection of the renal mass. To our knowledge, we present here the most detailed, challenging, and complicated laparoscopic nephron-sparing surgery yet to be reported with a diagnosis of metanephric adenoma in the central location.

BRAF mutations in metanephric adenoma of the kidney

BACKGROUND

Metanephric adenoma (MA) of the kidney is a rare, indolent tumor that may be difficult to differentiate from other small renal masses (SRMs). Genetic alterations associated with MA remain largely unknown.

OBJECTIVE

We aimed at defining genetic events in MA of the kidney and determining their influence in the management of this disease.

DESIGN, SETTING, AND PARTICIPANTS

Multiplexed mass spectrometric genotyping was performed on 29 MA cases after tumor DNA extraction. We also conducted a mutational screen in an additional 129 renal neoplasms. Immunohistochemistry was performed on the MA cases to assess molecular markers of signaling pathway activation. Patients' baseline characteristics, as well as follow-up data, were captured.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We used descriptive statistics for baseline clinical characteristics and incidence of mutations. The Wilcoxon rank-sum test was used to correlate patient characteristics with mutational status.

RESULTS AND LIMITATIONS

We identified the v-raf murine sarcoma viral oncogene homolog B1 (BRAF) V600E mutation in 26 of 29 MA cases. These results were validated in all cases using the commercially available BRAF Pyro Kit (QIAGEN). In contrast, BRAF mutations were rare in the other 129 non-MA renal neoplasms that were screened. We detected a BRAF mutation (V600E) in only one papillary renal cell carcinoma case. In all MA tumors, we documented expression of phosphorylated mitogen-activated protein kinase and phosphorylated extracellular signal-regulated kinase, accompanied by immunoreactivity for p16 (INK4a). All patients were treated with a partial or radical nephrectomy, and after a median follow-up of 26.5 mo, there were no local or distant recurrences. Limitations include the retrospective nature of this study.

CONCLUSIONS

BRAF V600E mutations are present in approximately 90% of all MA cases, serving as a potential valuable diagnostic tool in the differential diagnosis of SRMs undergoing a percutaneous biopsy. The presence of BRAF V600E and mitogen-activated protein kinase activation in a largely benign tumor supports the necessity for secondary events (e.g., p16 loss) in BRAF-driven oncogenesis.

Conservative treatment of metanephric adenoma. A case report and review of the literature

Metanephric adenoma (MA) is a rare kidney tumor, especially in children, with an excellent prognosis and frequent association with polycythemia. We report the case of a 4-year-old girl presenting a MA revealed by polycythemia. Any secondary polycythemia requires checking for a possible kidney tumor even when the erythropoietin level is not elevated. MA is an exclusively epithelial tumor that can be similar to nephroblastoma or papillary renal cell carcinoma; therefore, it requires strict histopathological analysis. There are few radiological characteristics of MA: well circumscribed tumor, slightly enhanced after the injection of an intravenous contrast medium on computed tomography scan or magnetic resonance imaging. Diagnosis can be supported by core-needle kidney biopsy after hemostasis check, following two published cases of associated acquired von Willebrand disease. Chemotherapy can then be avoided and first-line conservative surgical treatment by partial nephrectomy can be considered, as in our patient's case. However, the marginal resection raised the question of frozen sections analysis of the margins. We recommend thorough follow-up visits, combining clinical examination, ultrasonography and, in the case of polycythemia, biological assays.

Metanephric adenoma in a 2-year-old child: case report and immunohistochemical observations

Renal metanephric adenoma (MA) is an extremely rare benign tumor, especially in children under the age of 12 years old. In this article, we report a case of MA that was incidentally discovered in a 2-year-old girl by ultrasound. Magnetic resonance scan revealed a mass of right kidney that was hypointense and hyperintense on T1- and T2-weighted images, respectively. Laparoscopic nephron-sparing surgery was carried out to remove the lesion. Histopathologic examination of the specimen revealed MA with clear surgical margins. Immunohistochemically, the tumor cells showed focal reactivity for CD56, pan-cytokeratin (AE1/AE3), and epithelial membrane antigen, and negative reactivity for Wilms' tumor 1 gene product. Meanwhile, the tumor stroma was diffusely positive for vimentin. We also review the literature regarding the clinical, imaging, and histopathologic features of this lesion in the pediatric population.

Metanephric adenoma of the kidney: an unusual diagnostic challenge

Although metanephric adenoma (MA) is a rare, benign neoplasm of epithelial cells, it is often difficult to distinguish this entity from other malignant neoplasms preoperatively. We report a case of a large renal mass for which preoperative diagnosis was indeterminate, with the differential diagnosis including Wilm’s tumor, MA, and papillary renal cell carcinoma (PRCC). Accurate postoperative differentiation of MA from PRCC is critical because adjuvant therapy is considered after surgical resection of PRCC tumors.

Imaging renal cell carcinoma with ultrasonography, CT and MRI

The increased use of abdominal imaging techniques for a variety of indications has contributed to more-frequent detection of renal cell carcinoma (RCC). Ultrasonography has been used to characterize the solid versus cystic nature of renal masses. This modality has limitations, however, in further characterization of solid tumors and in staging of malignancy, although contrast-enhanced ultrasonography has shown promise. Cross-sectional imaging with multiplanar reconstruction capability via CT or MRI has become the standard-bearer in the diagnosis, staging and surveillance of renal cancers. The use of specific protocols and the exploitation of different imaging characteristics of RCC subtypes, including variations in contrast agent timing, MRI weighting and digital subtraction, have contributed to this diagnostic capability. Cystic renal masses are a special case, evaluation of which can require multiple imaging modalities. Rigorous evaluation of these lesions can provide information that is crucial to prediction of the likelihood of malignancy. Such imaging is not without risk, however, as radiation from frequent CT imaging has been implicated in the development of secondary malignancies, and contrast agents for CT and MRI can pose risks, particularly in patients with compromised renal function.