Is a large breast mass or cancer likely to have been missed on the mammogram?

Likelihood of Missed Large Mass or Cancer on Mammography

While mammography is highly sensitive for breast cancer detection (92-100%), it is extremely unlikely but not impossible for a large mass or cancer to be missed, particularly in women with dense breasts or when cancer presents as subtle architectural distortion rather than a discrete mass. 1

Understanding Mammographic Sensitivity and Limitations

The combined negative predictive value of mammography with ultrasound for palpable masses ranges from 97.4% to 100%, meaning that when both studies are negative, the chance of missing cancer is very low (0-2.6%). 2 However, negative imaging should never overrule a strongly suspicious clinical finding—any highly suspicious breast mass detected by imaging or palpation should undergo biopsy. 1

Factors That Increase Risk of Missed Cancer

Breast density significantly impacts mammographic sensitivity:

• Dense breast tissue can mask underlying lesions due to overlapping fibroglandular tissue 3
• Mammography may be less effective in women with dense breasts, though specific failure rates vary 2

Presentation patterns associated with missed cancers:

• Cancers visible on only one mammographic view are more commonly missed 3
• Architectural distortion without a discrete mass is more subtle and easier to overlook 4, 5
• Asymmetric breast tissue without associated microcalcifications or mass formation is concerning only when associated with a palpable abnormality 5

Cancer Characteristics When Detected

Most breast cancers demonstrate recognizable features:

• Approximately 80% of invasive cancers appear as irregular masses with spiculated or indistinct margins 1
• Suspicious microcalcifications are present in about 80% of ductal carcinoma in situ (DCIS) cases 1
• Mass lesions (with or without calcifications) are more likely to represent invasive cancer with potential nodal involvement compared to calcifications alone 6

Clinical Context Matters

For symptomatic presentations (palpable mass, focal pain, nipple discharge):

• If mammography is negative but clinical suspicion remains high, ultrasound should be performed 2
• If both mammography and ultrasound are negative but clinical findings are highly suspicious, biopsy is still warranted 2
• Studies show that among palpable masses with negative mammography and ultrasound, subsequent MRI has very low yield (PPV 13-25%), and most do not represent malignancy 2

For screening-detected abnormalities:

• BI-RADS Category 0 (incomplete assessment) requires additional imaging before final categorization 2
• Digital breast tomosynthesis (DBT) reduces recall rates for asymmetries compared to standard mammography (2.5% vs 3.4%) while maintaining similar cancer detection rates 3
• The malignancy rate for recalled asymmetries is low (1.7%) for both DBT and standard mammography 3

Common Pitfalls in Interpretation

Benign conditions frequently mistaken for malignancy include:

• Fibrocystic breast disease, surgical scars, radial scars, and focal sclerosis 7
• Asymmetric breast tissue without mass formation, microcalcifications, or architectural distortion represents normal variation unless associated with palpable abnormality 5

True cancers most commonly missed include:

• Infiltrating lobular carcinoma (more common with DBT-detected asymmetries) 3
• Low-grade carcinomas presenting with subtle microcalcifications 7
• Cancers presenting as architectural distortion alone 3

Bottom Line

A truly large breast mass is very unlikely to be completely missed on mammography, as size correlates with visibility. 6 However, if clinical concern persists despite negative imaging, the clinical examination takes precedence and tissue diagnosis should be pursued. 2, 1 The combination of mammography and ultrasound provides excellent negative predictive value, but no imaging modality is 100% sensitive, particularly in dense breasts or for subtle presentations like pure architectural distortion.