Which statement best describes the sonographic appearance of a simple cyst?

• A. Round or oval shape with sharp borders, smooth thin walls, anechoic, posterior enhancement
• B. Irregular border with internal septations
• C. Hypoechoic mass with internal vascular flow
• D. Solid mass with posterior shadowing

Answer: (A)

A simple cyst on breast ultrasound is fluid-filled, so it appears completely anechoic (black) with no internal echoes. It has a round or oval shape, with smooth, thin, well-defined walls, and shows posterior acoustic enhancement because sound travels easily through fluid, making the area behind the cyst look brighter. There should be no internal septations and no vascular flow on Doppler. This combination of anechoic content, round/oval shape, smooth thin walls, and posterior enhancement is the classic description of a simple cyst. The other patterns—irregular borders with septations, a hypoechoic mass with internal blood flow, or a solid mass with posterior shadowing—suggest complex or solid lesions rather than a simple cyst.