Nonpalpable Mammographic Findings
From the American College of Radiology
"With improved imaging techniques, screening mammograms enable early detection of smaller cancers. Most lesions detected mammographically are benign. Noncalcified lesions of concern on screening mammograms include masses, bilateral masses, focal asymmetries, and architectural distortions.
Benchmark data based on information from the Breast Cancer Surveillance Consortium (BCSC) report a positive predictive value (PPV3) in 33% of biopsies performed [1]. The mean cancer detection rate reported for screening mammography is 4.7/1,000 mammograms, with a mean invasive cancer size of 13 mm [2,3].
Normal soft-tissue can simulate a mass or focal asymmetry, and additional mammographic and/or ultrasound (US) evaluation may be necessary to determine the presence of a true finding.
Masses are three-dimensional structures with convex outward contours. Focal asymmetries are seen on two views but are non-mass-like, often with concave outward contours. If new or enlarging on screening mammography, these should be further evaluated with diagnostic imaging and possibly US. [4-7]. When a mass is detected mammographically, its shape, margin, density, and size should be assessed as outlined in the Breast Imaging Reporting and Data System: ACR BI-RADS-Mammography, 4th Edition (ACR BI-RADS® Atlas) [7-12].
Ultrasound US can be used to evaluate the cystic versus solid nature of a breast mass. Adhering to strict criteria, this technique can separate cystic from solid masses with an accuracy approaching 100% [10]. Using good-quality, high-frequency equipment, cysts as small as 2-3 mm in diameter can be demonstrated. However, cysts smaller than 8 mm or deeper than 3 cm from the skin can be difficult to characterize as anechoic [13,14].
After final mammographic evaluation, round or oval masses with circumscribed, partially obscured, indistinct, or microlobulated margins can be further investigated with US to characterize simple cysts, complicated cysts, complex cystic and solid masses, and solid masses [15]. Solid masses can often be further subcategorized as either probably benign (allowing short-term surveillance rather than biopsy) or suspicious, based on multiple sonographic parameters [15-17].
Masses with mammographic features that are suspicious or highly suggestive of malignancy, or masses with suspicious or typically benign calcifications, do not require US for assessment, although US can be used to guide needle biopsy if the mass is seen sonographically [15]. US is also useful in evaluating architectural distortions and asymmetries that cannot be dismissed as superimposed tissue after diagnostic mammographic evaluation. US can often confirm the suspicious nature of the finding and can guide biopsy.
In cases where the diagnostic workup of such a finding fails to show a persistent suspicious lesion, US can provide additional confirmation of the benign nature of the initial finding when thorough scanning is negative or when a benign sonographic explanatory correlate can be found. However, if a suspicious mammographic finding remains after diagnostic evaluation, negative US should not dissuade biopsy. Elastography, which examines the viscoelastic properties of tissue, is being evaluated as a way to increase the specificity of US, especially regarding evaluation and management of solid masses [18]. "
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