What are the radiographic appearances of breast cancer on a mammogram?

Mammographic Appearance of Breast Cancer

Breast cancer most characteristically appears on mammography as a spiculated mass (an irregular density with radiating lines extending from the margins) or as pleomorphic microcalcifications, particularly when clustered or grouped. 1

Primary Malignant Features

Spiculated Masses

• Spiculated masses represent the classic mammographic sign of invasive breast cancer, presenting as irregular densities with radiating lines extending outward from the margins 1
• These masses typically have irregular or indistinct borders rather than smooth, well-defined margins 2
• The spiculations reflect the infiltrative growth pattern of invasive carcinoma extending into surrounding breast tissue 1

Microcalcifications

• Pleomorphic microcalcifications carry a ≥95% probability of malignancy when clustered or grouped 1
• Calcifications are the most common mammographic finding in ductal carcinoma in situ (DCIS), present in approximately 80-90% of cases 1, 2
• Fine linear or fine-linear branching calcifications are characteristic of high-grade DCIS with necrosis 1, 2
• Malignant calcifications are typically fine, pleomorphic, and demonstrate linear branching patterns, contrasting with benign calcifications which are larger, coarser, and round with smooth margins 3

Distribution Patterns Matter

• The shape of calcification clusters is often irregular or triangular, suggesting segmental or ductal distribution, which is highly concerning for malignancy 1, 2
• Grouped or clustered distribution of microcalcifications increases suspicion compared to scattered or diffuse patterns 3

Secondary Suspicious Features

Architectural Distortion

• Focal architectural distortion without an associated mass can represent early breast cancer 4
• Women with architectural distortion on mammography have more than twice the risk of subsequent breast cancer compared to those with masses (aHR 2.21) 5

Asymmetries

• Focal asymmetry (increased density in one breast compared to the corresponding area in the opposite breast) requires further evaluation 1, 6
• Asymmetries can indicate breast cancer, though most are benign or caused by summation artifacts from tissue superimposition 6
• Women with asymmetries have 1.66 times higher risk of subsequent breast cancer compared to those with masses 5

Other Findings

• Multiple findings on a single mammogram increase suspicion and carry 1.89 times higher risk of subsequent breast cancer 5
• Skin thickening, particularly when diffuse and associated with trabecular distortion, can indicate inflammatory breast cancer 1

BI-RADS Risk Stratification

• BI-RADS 5 indicates ≥95% probability of cancer and includes spiculated masses and malignant-appearing pleomorphic calcifications 1
• BI-RADS 4 indicates suspicious findings with 2-95% probability of malignancy, warranting biopsy consideration 1

Critical Clinical Pitfalls to Avoid

Never Override Clinical Suspicion

• Approximately 10-16% of DCIS cases may have negative or minimal mammographic findings 1
• Never allow negative imaging to override a clinically suspicious palpable mass—any highly suspicious breast mass detected by imaging or palpation should undergo biopsy 1, 2
• A common error is assuming a palpable mass is benign simply because it is not visible on mammography (false negative) 7

Technical Requirements

• Magnification views are essential for proper characterization of calcifications and should be obtained routinely when microcalcifications are detected 1
• High-quality images and magnification views are required for detection and analysis of microcalcifications 3
• Spot compression and additional oblique views help differentiate recurrent tumor from postoperative changes 8

Density Limitations

• Dense breast tissue can mask lesions, and additional imaging modalities (ultrasound, MRI) may be needed in high-risk patients with dense breasts 1
• Digital breast tomosynthesis can address limitations of standard mammography by decreasing the lesion-masking effect of overlapping normal tissue 2

Imaging Performance Characteristics

• Mammography has 92-100% sensitivity and 90-96% specificity for breast cancer detection overall 1, 2
• For DCIS specifically, mammography is more sensitive (55%) than ultrasound (47%) due to superior visualization of microcalcifications 1, 2
• MRI has higher sensitivity for detecting high-grade DCIS compared to mammography (92% vs 56%) 2