Which statement best describes a simple cyst on ultrasound?

• A. Anechoic Interior With Posterior Acoustic Enhancement And Smooth Wall
• B. Heterogeneous Internal Echoes With Solid Components
• C. Irregular Thick Wall With Calcifications
• D. Mixed Fluid And Solid Components With Vascularity

Answer: (A)

A simple cyst on ultrasound is defined by anechoic contents, meaning it shows no internal echoes because the fluid Transmits sound easily. The posterior acoustic enhancement occurs because the fluid allows more sound to pass through and be brighter on the far side, creating a brighter area behind the cyst. The wall is thin and smooth with well-defined margins and no internal septations or solid components. These features together indicate a simple fluid-filled structure with no solid tissue or debris.

In contrast, the other patterns describe more complex or solid lesions: heterogeneous internal echoes with any solid components suggest a complex cyst or a solid mass; an irregular thick wall with calcifications raises suspicion for leakage, scar, or malignancy features; mixed fluid and solid components with vascularity indicate a complex lesion with blood flow, not a simple cyst.