From the Guidelines
Adrenomedullary cysts have specific imaging characteristics that help differentiate them from other adrenal lesions, and the most recent and highest quality study 1 suggests that CT scans are the most appropriate initial imaging modality. On CT scans, these cysts typically appear as well-defined, thin-walled, homogeneous, non-enhancing lesions with water density (0-20 Hounsfield units) 1. They may contain calcifications in the cyst wall in approximately 15% of cases. On MRI, adrenomedullary cysts demonstrate low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, consistent with their fluid content 1. They show no enhancement after contrast administration except for possible rim enhancement of the cyst wall. Ultrasound typically reveals an anechoic lesion with posterior acoustic enhancement. These cysts can vary in size from a few millimeters to over 20 cm, though most are between 3-6 cm. They are usually unilateral but can occasionally be bilateral. The imaging appearance may be complicated by hemorrhage within the cyst, which can alter the density on CT and signal characteristics on MRI. Adrenomedullary cysts are typically asymptomatic and found incidentally, with imaging characteristics helping to distinguish them from other adrenal pathologies such as adenomas, pheochromocytomas, or adrenal carcinomas. Some key points to consider when evaluating adrenal incidentalomas include:
- The size and density of the lesion on CT scan
- The presence or absence of enhancement on CT or MRI
- The presence or absence of calcifications or other characteristic features
- The clinical history and risk factors for malignancy
- The need for follow-up imaging and hormonal screening. The use of CT scans with delayed enhancement is also recommended 1 to help differentiate between benign and malignant lesions. Additionally, MRI with chemical shift imaging can be useful in characterizing adrenal lesions, particularly in cases where CT is indeterminate 1. It's worth noting that the management of adrenal incidentalomas can be complex and may require a multidisciplinary approach, taking into account the patient's overall health, medical history, and risk factors for malignancy 1. In general, the goal of imaging is to provide accurate characterization of the lesion and to guide further management, whether that involves surveillance, biopsy, or surgical intervention. Ultimately, the choice of imaging modality and the approach to management will depend on the individual patient's circumstances and the specific characteristics of the lesion 1.
From the Research
Imaging Characteristics of Adrenomedullary Cysts
- Adrenal cysts, including adrenomedullary cysts, are rare lesions representing approximately 1-2% of adrenal incidentalomas 2.
- The radiological appearance of an adrenal cyst is generally similar to that of cysts in the kidney, with characteristics such as:
- On imaging, most cysts are round/oval (85.4%), homogenous (83.2%) lesions with calcifications (64.0%) and no vascular enhancement (97.7%) 3.
- Adrenal cysts can be classified into pseudocysts, endothelial cysts, epithelial cysts, and parasitic cysts, with pseudocysts being the most common clinically recognized adrenal cysts in surgical series 4.
Diagnostic Imaging Modalities
- Radionuclide imaging, including (131)I-norcholesterol, (131)I-metaiodobenzylguanidine (MIBG), and (18)F-FDG PET scans, can provide significant functional information for tissue characterization 5.
- Norcholesterol and MIBG scans are able to detect benign tumors such as adenoma and pheochromocytoma, respectively 5.
- FDG PET allows for recognition of malignant adrenal lesions 5.
- Adrenal scintigraphy is recommended for tumor diagnosis and, hence, for appropriate treatment planning, particularly when CT or MRI findings are inconclusive for lesion characterization 5.