MRI of metanephric adenoma

Case Report: MRI, CEUS, and CT Imaging Features of Metanephric Adenoma with Histopathological Correlation and Literature Review

The metanephric adenoma is an extremely rare, benign, embryonal-epithelial neoplasm of the kidney and has a good prognosis with appropriate treatment. It can present at any age and is often asymptomatic. Histologically, the lesion is well established; however, there have been only a few cases described with available detailed imaging findings, most of them with large renal masses typically depicted by computed tomography (CT). This case report includes imaging of contrast-enhanced MRI, contrast-enhanced ultrasound (CEUS), and CT, and thus adds to the information available, potentially promoting a nephron-sparing clinical pathway. We report on the clinical presentation, imaging, histopathological diagnosis, and treatment data of a 27-year-old female, in whom an incidental, symptomatic kidney tumor was detected. CT, CEUS, and MRI showed a suspicious unifocal renal lesion with inhomogeneous enhancement, which was indistinguishable from renal cell carcinoma. After laparoscopic resection, a metanephric adenoma with microscopically partially glandular, partially nest-like solid growth and without distinctive atypia was diagnosed pathohistologically. Immunohistochemistry results were positive for Wilms Tumor 1 and CD57 and negative for EMA and CK7: 2–3% positive cells in MIB1 coloring. At 3-month and 1-year follow-up, the patient was asymptomatic and imaging showed no recurrence of renal masses or metastases.

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.

Metanephric Adenoma of the Kidney with Massive Hemorrhage and Necrosis: Immunohistochemical, Ultrastructural, and Flow Cytometric Studies

Metanephric adenoma of the kidney is rare. We report 2 cases of metanephric adenoma with massive hemorrhage and necrosis. Case 1, a 42-year-old Japanese woman, complained of abdominal pain. Case 2, a 41-year-old Japanese woman, complained of fever and lumbago. They underwent nephrectomy. The cut surface was solid and yellow with massive hemorrhage and necrosis. These tumors showed packed tubular and glomeruloid patterns. The tumor cells were uniform and small, with uniform, oval, and hyperchromatic nuclei and scant cytoplasm, and showed reactivity for cytokeratin, vimentin, and CD 57. The MIB-1 indexes were up to 0.63%. The DNA ploidy pattern was diploid. The tumor cells formed small tubular structures with lumina and microvilli. These features suggested that metanephric adenoma is a benign tumor of an immature epithelial nature.

The Clinical Characteristics of Metanephric Adenoma: A Case Report and Literature Review

We describe the clinical presentation, diagnosis, treatment, and follow-up data of a 39-year-old woman with asymptomatic right kidney tumor, which was later histopathologically diagnosed as metanephric adenoma (MA). Macroscopically, the tumor had integrity tegument with homogeneous and gray cutting surface. Microscopically, the tumor cells were formed in adenoid or papillary pattern and contained psammoma bodies, without distinctive atypia. Immunohistochemistry results showed they were negative for creatine kinase 7, epithelial membrane antigen, and renal cell carcinoma, and positive for AE1/AE3, vimentin, and Wilms Tumor 1. Pathological diagnosis was MA. The 48 months' follow-up information was available without recurrence.According to this case and literature review, we figured that it is difficult to make a definite diagnosis of MA only by image examination. Nephron-sparing surgery is eligible to treat MA. Long-term active surveillance is necessary because of the uncertainty of the biological behavior and cellular origin of MA.

METANEPHRIC ADENOMA DIAGNOSED PREOPERATIVELY AS RENAL CELL CARCINOMA: A REPORT OF TWO CASES

Metanephric adenoma is an extremely rare benign tumor. We report two cases of metanephric adenoma that were diagnosed preoperatively as renal cell carcinoma (RCC).Case 1 was a right renal tumor found by ultrasonography in a 57-year old woman who presented for a medical examination. Abdominal CT revealed a 26-mm mass that was enhanced weakly in the early phase and enhanced strongly in the late phase, in the right kidney. Based on a clinical diagnosis of RCC (cT1aN0M0), laparoscopic partial nephrectomy was performed. Case 2 was a left renal tumor incidentally found during an annual examination of a 79-year old woman with a past history of breast cancer. Abdominal CT revealed a 24-mm mass that was enhanced heterogeneously in the left kidney. Based on a clinical diagnosis of RCC (cT1aN0M0), laparoscopic radical nephrectomy was performed. The pathological diagnosis of both cases was metanephric adenoma.It is often difficult to distinguish metanephric adenoma from other malignant neoplasms preoperatively. When it is difficult to distinguish between renal cell carcinoma and metanephric adenoma, renal tumor biopsy and minimal surgery is required.

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.

The imaging features of metanephric adenoma: a case report and review of literature

Metanephric adenoma (MA) is a rare epithelial tumor of the kidney with a characteristic histology. To date, the imaging features of the tumor have not been clearly described. Until now, MA was considered to be benign, but the majority of MA cases underwent nephrectomy. Here, we report a case of MA confirmed by surgical pathology, and we will analyze the ultrasound and computed tomography findings. The radiological features of MA are presented along with a brief review of the pertinent literature to deepen the understanding of MA’s imaging features.

Imaging findings of common benign renal tumors in the era of small renal masses: differential diagnosis from small renal cell carcinoma: current status and future perspectives

The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging. A large proportion of these SRMs are not malignant, and do not require invasive treatment such as nephrectomy. Therefore, differentation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management. This article reviews the radiological features of benign SRMs, with focus on two of the most common benign entities, angiomyolipoma and oncocytoma, in terms of their common imaging findings and differential features from RCC. Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.

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.

Renal metanephric adenoma mimicking papillary renal cell carcinoma on computed tomography: a case report

We present a case of renal metanephric adenoma (MA) mimicking papillary renal cell carcinoma (PRCC) on computed tomography (CT). In the present case, double-phase enhanced CT showed a hypovascular right renal tumor with gradual and prolonged enhancement. The renal tumor was surgically removed. Histological examination of the resected specimen showed renal MA. Although the radiological features of renal MA have been described by some authors, only a few reports have mentioned the pattern of enhancement on multiphase enhanced CT. The pattern of enhancement of a renal tumor is likely to be correlated with its pathological features. Since renal MA is thought to be genetically related to PRCC, these two tumors are likely to demonstrate similar radiological features, so that differentiating between them becomes difficult. In patients with a hypovascular renal mass that shows gradual and prolonged enhancement on multiphase enhanced CT, the diagnosis of renal MA should be considered.

CT and ultrasound findings of metanephric adenoma: a report of two cases and literature review

Metanephric adenoma (MA) of the kidney is an uncommon benign epithelial tumour that can present at any age. The histology of the lesion is well established, but imaging findings have been described in only a few cases. We report the CT and ultrasound appearance of MA in two females to increase the awareness of this entity among radiologists. Its recognition may facilitate nephron-sparing surgery.

Magnetic resonance imaging of renal masses

The increasing frequency of incidentally detected renal masses supports the need for accurate imaging characterization to avoid unnecessary surgery/interventional procedures. Furthermore, the need for accurate presurgical diagnosis of specific histologic subtypes of renal malignancies is increasingly important as advances in understanding of tumor biology direct targeted courses of therapy. Magnetic resonance imaging is uniquely suited for the evaluation of renal masses because of its ability to provide excellent soft-tissue contrast and demonstration of enhancement, as well as its multiplanar capabilities. Although the spectrum of masses that may occur in the kidneys is broad, specific imaging features may assist in their accurate diagnosis. Examples of the imaging appearance of common and uncommon renal masses are provided along with a protocol for comprehensive magnetic resonance examination of the kidneys.

Benign renal neoplasms in adults: cross-sectional imaging findings

OBJECTIVE

A broad spectrum of benign renal neoplasms in adults shows characteristic ontogeny, histology, and tumor biology. Benign renal tumors are classified into renal cell tumors, metanephric tumors, mesenchymal tumors, and mixed epithelial and mesenchymal tumors. Select benign tumors show characteristic anatomic distribution and imaging features. However, because of overlapping of findings between benign and malignant renal tumors, histologic evaluation may be required to establish a definitive diagnosis. Accurate preoperative characterization facilitates optimal patient management.

CONCLUSION

We attempt to provide a comprehensive, contemporary review of benign renal neoplasms that occur in adults, focusing on cross-sectional imaging characteristics.

Metanephric Adenoma of the Kidney: Case Report and Review of the Literature

Metanephric adenoma is a rare tumor of the kidney. So far metanephric adenomas were considered to be benign, slowly growing and non-metastasizing tumors with an excellent prognosis. Only recently two cases of metastasized metanephric adenomas were published. Therefore, diagnostic work up, therapy and follow up of this tumor have to be reassessed. We report the case of a 42 year old male with metanephric adenoma. Current literature concerning metanephric adenoma is reviewed.

Metanephric adenoma treated with laparoscopic nephrectomy

A 31-year-old-female presented with a left renal mass detected incidentally during an abdominal ultrasound examination. Computed tomography and angiography revealed a hypovascular solid tumor 4.5 cm in diameter at the middle portion of the left kidney. Laparoscopic left nephrectomy was performed and macroscopic examination of the specimen revealed encapsulated tumor with grayish yellow cut surface. Histological examination demonstrated that the tumor cells were small scant cytoplasms, containing round and regular nuclei, forming a glomerular-like structure. There was no mitosis nor cellular atypia indicating a malignant structure. The histological diagnosis was metanephric adenoma.

Double-phase helical CT of small renal parenchymal neoplasms: correlation with pathologic findings and tumor angiogenesis

PURPOSE

To correlate the enhancement pattern of double-phase helical computed tomography (CT) of small renal parenchymal neoplasms with pathologic findings and tumor angiogenesis, and evaluate whether the enhancement pattern would be useful in differentiating the histomorphologic types of small renal parenchymal neoplasms.

MATERIALS AND METHODS

Double-phase helical CT (5 mm slice) of the corticomedullary phase (CMP) and late nephrographic phase (NP) was performed in 40 surgically resected renal neoplasms <3.5 cm. The patterns of CT attenuation value and homogeneity were correlated with the subtypes of neoplasms, microvessel density, and the existence of intratumoral necrosis or hemorrhage.

RESULTS

Clear cell renal cell carcinomas (RCC) (n = 29) showed a peak attenuation value in the CMP of >100 HU [Hounsfield units]. Chromophobe cell RCC (n = 2) showed a peak attenuation value in the CMP of <100 HU. Papillary RCC (n = 5) showed a gradual enhancement with the attenuation value in the CMP of <100 HU. However oncocytomas (n = 2) and metanephric adenomas (n = 2) also showed patterns similar to these subtypes of RCC. The degree of enhancement in the CMP correlated with microvessel density (r = 0.87). All tumors with an homogeneous enhancement pattern did not show necrosis or hemorrhage on histologic specimen.

CONCLUSION

The enhancement pattern in double-phase helical CT was different among the subtypes of RCC, and correlated with microvessel density or the existence of intratumoral necrosis or hemorrhage. However it did not differentiate between RCC and other solid tumors.

Metanephric adenoma

A 59-year old woman was diagnosed with a tumour in her right kidney. A nephrectomy was performed, and a 45 mm diameter tan-pink coloured tumour was found. Microscopy revealed small, dark cells in organized arrays of small round acini and tubules with glomeruloid infoldings. A diagnosis of metanephric adenoma was made. The tumour cells proved diploid on flow cytometry and immunohistochemical staining was positive for CAM 5.2 and AE-3. FISH analysis of three chromosomes did not reveal any abnormal karyotype. It is important to differentiate metanephric adenoma from renal cell carcinoma and adult Wilm's tumour, since it has a benign course.