Diagnostic Testing to Confirm a Cyst

Ultrasound is the first-line imaging modality for diagnosing cysts, with MRI being superior to CT for further characterization when needed. 1

Initial Diagnostic Approach

Ultrasound should be the first diagnostic test used for suspected cysts, particularly for hepatic cysts, as it can reliably identify simple cysts with their characteristic features: anechoic appearance, sharp and smooth borders, thin walls, and strong acoustic posterior enhancement 1
For pancreatic cysts, contrast-enhanced MRI with MRCP (magnetic resonance cholangiopancreatography) is generally preferred over CT due to its superior soft-tissue resolution and ability to demonstrate ductal communication 1
For breast cysts, ultrasound is recommended as the initial diagnostic imaging, especially for women younger than 30 years presenting with a dominant mass 1

Appear as anechoic (cystic), well-circumscribed, round or oval with well-defined imperceptible wall and posterior enhancement on ultrasound 1
No further imaging is typically needed if ultrasound confirms a simple cyst 1
Simple cysts typically follow an indolent course without significant changes in size over time 1

Complicated cysts contain low-level echoes or intracystic debris but no solid elements 1
Complex cysts have discrete solid components, which may include thick walls, thick septa, and/or intracystic masses 1
Complex cysts have both anechoic (cystic) and echogenic (solid) components and carry a higher risk of malignancy 1

MRI is superior to CT for characterizing cysts and reproduces ultrasound-defined features better 2
For pancreatic cysts, MRI with MRCP has a diagnostic accuracy of 73.2% to 91% for distinguishing between malignant and nonmalignant lesions 1
For soft tissue cysts, MRI with contrast is mandatory if a cyst demonstrates wall thickening or internal complexity 3
For hepatic cysts, MRI is particularly useful for diagnosing cyst hemorrhage, showing heterogeneous hyperintensity on both T1- and T2-weighted sequences 1

CT is less accurate than MRI for cyst characterization but may be used when MRI is contraindicated 1
For pancreatic cysts, dual-phase contrast-enhanced pancreatic protocol CT can provide critical diagnostic information about calcifications, ductal dilation, septations, and mural nodules 1
CT is not recommended for diagnosing cyst hemorrhage 1

For pancreatic cysts with worrisome features (≥3 cm size, thickened/enhancing wall, nonenhancing mural nodule, main pancreatic duct 5-9 mm), EUS-FNA is recommended 1
EUS-FNA allows for biochemical and cytological analysis of cyst fluid, which can help distinguish mucinous from non-mucinous lesions 1

Diagnostic criteria include: cyst aspiration showing evidence of infection, fever >38.5°C for >3 days, CT/MRI detecting gas in a cyst, increased FDG activity on PET-CT, tenderness in the affected area, increased CRP, increased leukocyte count, and positive blood culture 1
Radiological findings include: debris with thick wall on ultrasound, enhanced wall thickening on CT/MRI, high signal intensity on diffusion-weighted MRI, and increased FDG activity on PET-CT 1

Ultrasound may show sediment or mobile septations 1
MRI is very specific, showing heterogeneous and intense signal on both T1- and T2-weighted sequences 1
CT is not recommended for diagnosing cyst hemorrhage 1

Solid benign and malignant masses can mimic cysts on imaging by exhibiting bright T2 signal on MRI 3
Any enhancement within a cystic-appearing lesion on contrast-enhanced MRI suggests a solid component and raises concern for malignancy 3
For pancreatic cysts, the presence of "worrisome features" or "high-risk stigmata" significantly increases malignancy risk and should prompt further evaluation 1
Serum tumor markers like CEA and CA19-9 cannot reliably distinguish between simple hepatic cysts and mucinous cystic neoplasms of the liver 1
Complex breast cysts have a relatively high risk of malignancy (14-23%) and should be evaluated by tissue biopsy 1