Metanephric adenoma overview

# Overview
Metanephric adenoma (MA)is a rare, benign tumor of the kidney. Metanephric adenoma was first described by Brisigotti, Cozzutto et al. in 1992. On gross pathology, a sharply circumscribed, nonencapsulated solitary mass is the characteristic finding of metanephric adenoma. On microscopic histopathological analysis, small uniform cells with fine chromatin and smooth nuclear membrane, variable architecture, and psammoma bodies are characteristic findings of metanephric adenoma. Metanephric adenoma may be caused by the allelic changes of tumor suppressor gene on chromosome 2p13. Metanephric adenoma must be differentiated from renal cell carcinoma and Wilm's tumor. The incidence of metanephric adenoma increases with age; the median age at diagnosis is 50-60 years. Females are more commonly affected with metanephric adenoma than males. The female to male ratio is approximately 2 to 1. Metanephric adenoma is often asymptomatic. Possible symptoms of metanephric adenoma include hematuria, abdominal distension, and abdominal pain. Surgery is the mainstay of treatment for metanephric adenoma. Prognosis of metanephric adenoma is generally excellent.

# Historical Perspective
Metanephric adenoma was first described by Brisigotti, Cozzutto et al. in 1992.

# Classification
There is no classification system established for metanephric adenoma.

# Pathophysiology
On gross pathology, a sharply circumscribed, nonencapsulated solitary mass is the characteristic finding of metanephric adenoma. On microscopic histopathological analysis, small uniform cells with fine chromatin and smooth nuclear membrane, variable architecture, and psammoma bodies are characteristic findings of metanephric adenoma.

# Causes
Metanephric adenoma may be caused by the allelic changes of a tumor suppressor gene on chromosome 2p13.

# Differential Diagnosis
Metanephric adenoma must be differentiated from renal cell carcinoma and Wilm's tumor.

# Epidemiology and Demographics
The incidence of metanephric adenoma increases with age; the median age at diagnosis is 50-60 years. Females are more commonly affected with metanephric adenoma than males. The female to male ratio is approximately 2 to 1.

# Risk Factors
There are no established risk factors for metanephric adenoma.

# Screening
According to the the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for metanephric adenoma.

# Prognosis
Prognosis of metanephric adenoma is generally excellent.

# Staging
There is no established system for the staging of metanephric adenoma.

# Diagnosis

## Symptoms
Metanephric adenoma is often asymptomatic. Possible symptoms of metanephric adenoma include hematuria, abdominal distension, and abdominal pain.

## Physical Examination
Physical examination of patients with metanephric adenoma is usually remarkable for a palpable abdominal mass.

## Laboratory Findings
Laboratory finding consistent with the diagnosis of metanephric adenoma is elevated red blood cells on urinalysis.

## X Ray
There are no X-ray findings associated with metanephric adenoma.

## CT
CT scan may be helpful in the diagnosis of metanephric adenoma. Findings on CT scan suggestive of metanephric adenoma include a hyperattenuating mass on unenhanced CT scan, hypovascular masses with frequent foci of hemorrhage and necrosis, and calcification.

## MRI
MRI may be helpful in the diagnosis of metanephric adenoma. Findings on MRI suggestive of metanephric adenoma include hypointense signal on T1 weighted image and slightly hyperintense on T2 weighted image.

## Ultrasound
Ultrasound may be helpful in the diagnosis of metanephric adenoma. A finding on ultrasound suggestive of metanephric adenoma is an expansile hypoechoic or hyperechoic mass.

## Other Imaging Findings
There are no other imaging findings associated with metanephric adenoma.

## Other Diagnostic Studies
There are no other diagnostic study findings associated with metanephric adenoma.

## Biopsy
Biopsy is helpful in the diagnosis of metanephric adenoma.

# Treatment

## Medical Therapy
The mainstay of therapy for metanephric adenoma is surgery.

## Surgery
Surgery is the mainstay of treatment for metanephric adenoma.

## Primary Prevention
There is no established method for prevention of metanephric adenoma.

## Secondary Prevention
There are no secondary preventive measures available for metanephric adenoma.