What does breast cancer look like during breast cancer screening?

The majority of breast cancers found by screening mammography are small and non-palpable. In contrast, breast cancers that are not detected by screening mammography tend to be much larger and usually are palpable. Breast cancer on mammography usually appears as a suspicious microcalcifications, a super-density with irregular borders, or an asymmetrical density compared with the other breast or the previous annual mammogram. On an ultrasound, breast cancer appears as a solid mass that is taller than wide with irregular borders or an angular or lobular borders. There is frequently increased vascularity within the solid mass and a shadow cast behind the mass.
 
Magnetic resonance imaging (MRI) is another modality for breast imaging. Breast cancer usually presents on MRI as a contrast-enhanced lesion. Breast MRI probably gives the best three-dimensional assessment of the tumor mass and also allows doctors to evaluate whether there are satellite lesions. MRI is significantly better than mammography for evaluating the lymph nodes in the armpit, behind the muscle and along the internal mammary chain. And MRI screening usually is restricted to women with high risk conditions for developing breast cancer.