Adrenal Mass
An “adrenal mass” identified on a radiology report refers to a growth located on one of the adrenal glands, which are positioned above the kidneys. These masses are commonly detected during imaging studies performed for unrelated reasons. This finding requires evaluation but is often benign. This article explains adrenal masses, their appearance on various imaging modalities, and the standard approach to their assessment and management.
What Is an Adrenal Mass?
An adrenal mass is a growth or tumor found on one of the adrenal glands. These small, triangle-shaped glands sit on top of each kidney and produce hormones that regulate metabolism, immune system, blood pressure, and stress response. Adrenal masses vary in size and can be benign (non-cancerous) or malignant (cancerous). The majority of adrenal masses discovered through imaging are benign adenomas that don’t cause symptoms.
How Common Are Adrenal Masses?
Adrenal masses are surprisingly common findings on imaging tests. They’re detected in approximately 5% of all abdominal CT scans performed for unrelated reasons. These incidental discoveries, often called “incidentalomas,” become more common as people age. By age 70, up to 7% of the population may have an adrenal mass that could be detected on imaging, though most never cause symptoms or health problems.
Types of Adrenal Tumors Found on Imaging
Different types of adrenal masses appear uniquely on imaging tests:
Adrenal Adenomas
Adenomas are the most common type of adrenal mass, accounting for about 80% of cases. They’re benign tumors that typically appear well-defined with smooth borders on imaging. On CT scans, many adenomas contain high fat content, giving them a distinctive appearance that helps radiologists identify them.
Pheochromocytomas
These rare tumors can produce excess adrenaline and noradrenaline hormones. On imaging, they often appear larger than adenomas with areas that may enhance strongly when contrast is administered during the scan.
Adrenal Carcinomas
Adrenal carcinomas are rare but serious cancerous tumors. On imaging, they typically appear large (often greater than 4 cm), irregularly shaped, and may show evidence of invasion into surrounding tissues.
Adrenal Metastases
Cancer that has spread from elsewhere in the body can appear as masses in the adrenal glands. These metastatic lesions often have irregular borders and vary in appearance depending on the primary cancer type.
Diagnostic Imaging for Adrenal Masses
Several imaging techniques help identify and characterize adrenal masses:
CT Scan Findings
CT (Computed Tomography) scans are often the first test to identify an adrenal mass. Key CT characteristics that radiologists evaluate include:
- Size of the mass (smaller masses are more likely benign)
- Density measurements (measured in Hounsfield Units or HU)
- Contrast enhancement patterns
- Presence of calcifications
- Growth rate if previous scans are available
Low-density adrenal masses (below 10 HU) on unenhanced CT often represent benign adenomas containing fat.
MRI Evaluation
MRI (Magnetic Resonance Imaging) provides excellent tissue characterization without radiation exposure. For adrenal masses, specific MRI sequences help distinguish benign from suspicious lesions:
- Chemical shift imaging detects microscopic fat present in most benign adenomas
- T2-weighted images help identify pheochromocytomas, which appear bright
- Contrast enhancement patterns reveal blood flow characteristics
PET Scan Interpretation
PET (Positron Emission Tomography) scans measure metabolic activity in tissues. Malignant adrenal masses typically show increased uptake of the radiotracer, appearing as “hot spots” on the scan. This helps differentiate between benign masses and those that might be cancerous.
When Should You Worry About an Adrenal Mass?
Certain imaging features raise concern about an adrenal mass:
Size Matters
Adrenal masses larger than 4 centimeters have a higher risk of being malignant. While many larger masses still prove benign, their size typically triggers additional evaluation.
Growth Rate
Rapid growth of an adrenal mass between imaging studies is concerning. Benign adenomas typically grow slowly or not at all, while malignant tumors often expand rapidly.
Irregular Appearance
Masses with irregular borders, heterogeneous (varied) internal structure, or invasion into surrounding tissues raise suspicion for malignancy on imaging studies.
Hormone Production
Some adrenal masses produce excess hormones that cause specific symptoms. While hormone production itself doesn’t determine if a mass is cancerous, it affects treatment decisions and timing.
Follow-Up Imaging Recommendations
When an adrenal mass is discovered, follow-up often includes:
Repeat Imaging
For small, benign-appearing masses, follow-up CT or MRI is typically recommended after 6-12 months to ensure stability. Lack of growth over time provides reassurance about benign nature.
Imaging Intervals
The appropriate interval between scans depends on the initial characteristics of the mass. Higher-risk masses may need earlier follow-up (3-6 months), while lower-risk findings might wait a full year before reimaging.
When Additional Testing Is Needed
If imaging characteristics are concerning or inconclusive, additional testing might include:
- Adrenal protocol CT (specialized technique to evaluate adrenal tissue)
- Chemical analysis for hormone production
- Biopsy (though this is performed selectively)
Treatment Approaches Based on Imaging
Treatment recommendations often depend on imaging characteristics:
Observation
Most small, benign-appearing adrenal masses can be safely monitored with periodic imaging. This approach avoids unnecessary surgery for masses that pose no health risk.
Surgical Removal
Surgery may be recommended when imaging suggests:
- Potential malignancy
- Significant hormone production
- Size greater than 4-6 cm
- Continued growth during observation
Conclusion
Finding an adrenal mass on imaging doesn’t automatically mean something serious, but it deserves appropriate attention and follow-up. Modern imaging techniques allow radiologists to characterize these masses with increasing precision, helping guide management decisions. If you’ve received a report mentioning an adrenal mass, discuss with your doctor what specific imaging characteristics were noted and what follow-up plan makes most sense for your situation. With proper evaluation and monitoring through imaging, adrenal masses can be managed effectively.
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