Final answer:
A lesion with smooth regular borders, an anechoic interior, and acoustic enhancement on ultrasonography is likely a simple cyst, as opposed to a fibroadenoma, abscess, or ductal carcinoma.
Step-by-step explanation:
The ultrasonography characteristics described in the question indicate that the lesion is likely a simple cyst. A spherical mass with smooth regular borders, an anechoic interior, and acoustic enhancement are typical features of a simple cyst. A fibroadenoma usually presents as a well-circumscribed, solid, and hypoechoic mass without posterior acoustic enhancement. An abscess would appear as a complex lesion, often with irregular borders and a complex interior due to the presence of pus. Lastly, ductal carcinoma is typically irregular, spiculated, and hypoechoic with possible posterior shadowing—characteristics that do not match the description given.