Non-mass finding (breast ultrasound)

A non-mass finding on breast ultrasound refers to a discrete region of altered breast parenchymal echotexture that does make a mass shape (i.e. non-identifiable in two planes). "Non-mass finding" is not a current BI-RADS descriptor. 

Terminology

Non-mass findings are described in numerous ways in the literature ^1-3:

• non-mass lesion
• non-mass-like lesion
• non-mass image-forming lesion
• vague area of altered echotexture
• duct-like structures
• focal shadowing

Epidemiology

Non-mass findings have been reported to occur in ~5% of diagnostic or screening breast ultrasound ⁴.

Pathology

The malignancy rate for non-mass findings on breast ultrasound is unknown. Wide variations in benign rate (46-90%) and malignancy rate (10-54%) have been reported ¹.

A wide range of benign and malignant conditions have been reported to represent non-mass findings including ^1,2,4:

• benign: fibrocystic change, stromal fibrosis
• malignant: high-grade DCIS, breast cancer (ductal, lobular)

Radiographic features

Ultrasound

Non-mass findings are focal, linear-segmental or regional areas of altered breast echotexture that do not make a mass shape ^1,2,4:

• hypoechoic, hyperechoic or mixed
• non-identified in two planes
• lack of conspicuous or biconvex margins
• lack of conspicuous shape

Associated features ^1,3:

• calcifications (most commonly associated with malignancy)
• acoustic shadowing
• architectural distortion
• tubal or ductal architecture

Mammography

The presence of ultrasound non-mass finding correlates of a mammographic finding (most commonly calcifications, asymmetric density, architectural distortion) are more associated with a malignant than benign pathology ¹.