On ultrasound, all breast tissue is compared to the echogenicity of which tissue?

• A. Muscle
• B. Breast fat
• C. Connective tissue
• D. Bone

Answer: (B)

In breast ultrasound, tissue echogenicity is judged against a familiar, constant reference: fat. Fat is the predominant, relatively uniform component of the breast, so comparing other tissues to fat provides a consistent baseline across patients and images. Describing a lesion as hypo-, iso-, or hyperechoic relative to fat lets radiologists quickly communicate how the lesion’s brightness compares to normal breast fat, which helps in characterization and management decisions. Other tissues like muscle, bone, or connective tissue aren’t used as the standard reference because their echogenicity isn’t representative of normal breast parenchyma—bone is very bright and shadowing-prone, muscle has a different texture, and fat offers the most reliable baseline.