Metanephric adenoma of the kidney

Metanephric adenoma treated with laparoscopic nephrectomy: A case report

Metanephric adenoma is an uncommon benign renal tumor that occurs predominantly in adult females and rarely in children. Its histomorphology resembles that of epithelial Wilms' tumor and papillary renal cell carcinoma. From a diagnostic and therapeutic perspective, recognition of this entity is important as it has a more favorable clinical outcome compared with Wilms' tumor and renal cell carcinoma. Metanephric adenoma should not be treated with nephrectomy if the tumor size is small. However, preoperative diagnosis of this disease is extremely challenging. The present study describes a case of this rare disease, which was treated with laparoscopic nephrectomy. The tumor was not clearly enhanced in the early phase on contrast-enhanced computed tomography imaging. The immunohistochemical analysis revealed positive immunoreactivity for vimentin and Wilms' tumor 1, and partial positivity for cytokeratin (CK) AE1/AE3, CK56, and CK34, consistent with metanephric adenoma. Although metanephric adenoma is difficult to diagnose preoperatively, this rare disease must be considered in order to avoid unnecessary surgical procedures in these patients.

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.

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.

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.

Radiofrequency-assisted partial nephrectomy for metanephric adenoma: a case report and literature review

Metanephric adenoma (MA) is a rare benign tumor, diagnosis of which is often carried out after surgical treatment. In case of peripheral lesions, a partial nephrectomy (PN)--either open or laparoscopic may be preferred--and, furthermore, a radiofrequency (RF)-assisted procedure may facilitate adequate hemostasis. In November 2010, the authors performed a RF-assisted PN, according to Habib's technique, using a 4-needle bipolar device, on a woman affected by a small exophytic MA of the right kidney. Fibrin glue was applied on the cut surface. Postoperative course was uneventful, and discharge was on postoperative day 4. MA is an extremely rare benign tumor with a favorable prognosis. In case of a preoperative cytological diagnosis, a careful follow-up has to be considered. PN represents the standard of care for small exophytic MA, and RF-assisted procedures allow an excellent hemostasis and a rapid conservative resection, with very low morbidity.

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.

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.

Local resection of metanephric adenoma with kidney preservation

Metanephric adenoma (MA) is a rare renal neoplasm present at any age. Usually, a total nephrectomy is performed. Some successful partial nephrectomies or selective tumor resections are described in adults but not in children. We present here the case of a 15-month-old boy, the youngest patient yet to be reported with an MA. We performed a local resection of the tumor. Today, 2 1/2 years after surgery, we can document a favorable clinical course and normal ultrasound findings in the follow-up of the operated kidney. This case gives further evidence that organ-sparing resection of MA is feasible in selected cases. A close clinical and ultrasound follow-up is mandatory for this approach.

Laparoscopic nephron-sparing surgery for metanephric adenoma

A 47-year-old patient presented with hematuria of 3-month duration. Computed tomography revealed right lower polar exophytic mass. Laparoscopic nephron-sparing surgery was performed. The macroscopic examination of the mass showed encapsulated tumor with soft pultaceous material. Histologic examination of the mass was consistent with metanephric adenoma. We are reporting this case of metanephric adenoma, being treated with laparoscopic partial nephrectomy.

Hyperattenuating renal masses: etiologies, pathogenesis, and imaging evaluation

Some renal masses have higher attenuation than the surrounding renal parenchyma at computed tomography (CT). Their hyperattenuation is usually the result of proteinaceous fluid or densely packed cells. Most hyperattenuating renal masses are benign hemorrhagic or proteinaceous cysts. However, solid enhancing hyperattenuating renal masses may have malignant as well as benign causes. Possible malignant causes include renal cell carcinoma and lymphoma; benign causes include angiomyolipoma with minimal fat. It is important to identify the cause of a hyperattenuating renal mass so as to avoid unnecessary surgical resection or ablation. CT may be useful for diagnosing benign hyperattenuating renal cysts, hematomas, and vascular anomalies that appear masslike. However, some solid, enhancing, hyperattenuating masses cannot be diagnosed confidently with CT alone: Small (< or = 3-cm-diameter), homogeneously enhancing, hyperattenuating renal masses depicted on CT images may be either benign angiomyolipomas with minimal fat or renal cell carcinomas. Magnetic resonance (MR) imaging may be helpful for differentiating between angiomyolipomas with minimal fat and clear cell renal cell carcinomas; however, differentiation between angiomyolipomas with minimal fat and papillary renal cell carcinomas often is not possible on the basis of MR imaging. In such cases, a percutaneous biopsy may be useful for diagnosis. If the results of MR imaging and percutaneous biopsy are not definitive, surgery is warranted.

Renal Masses in the Adult Patient: The Role of Percutaneous Biopsy

Although percutaneous renal mass biopsy with cross-sectional imaging guidance has long been considered to be safe and accurate, there have been recent advances in imaging, interventional, and cytologic techniques that have increased the role of percutaneous biopsy in the diagnosis of renal masses. Today, biopsy plays a fundamental role in the care of patients with a renal mass. Biopsy results are used to confirm the diagnosis of renal cancers, metastases, and infections, and there is increasing evidence to suggest that biopsy can help subtype and grade many primary renal cancers. Because a considerable fraction of small solid renal masses are benign and do not need treatment, there is an increasing need to diagnose them. Biopsy after a full imaging work-up can help prevent unnecessary and potentially morbid surgical and ablation procedures in a substantial number of patients. Although more data are needed to understand the overall accuracy of biopsy for the diagnosis of benign lesions, many can be diagnosed with the aid of biopsy findings. This article reviews reported experience with percutaneous renal mass biopsy, discusses the technical factors that contribute to results, and details seven specific clinical settings that should prompt the clinician to consider percutaneous biopsy when encountering a renal mass.