Pectoralis Invasion on Breast MRI

IMAGING FINDINGS: ​
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Sagittal MRI image demonstrates an irregular enhancing mass in the inferior right breast at a posterior depth. There is enhancement of the underlying pectoralis muscle consistent with pectoralis invasion.
 
WHY IT MATTERS:

1. Breast MRI is frequently used to map out the extent of disease in a newly diagnosed breast carcinoma.
   
2. Pectoralis or chest wall invasion are important factors for the surgeon and oncologist.  This can alter surgical planning and treatment options.
   
3. Occasionally, a mass will “abut the pectoralis muscle without definite invasion.” But if there is enhancement of the pectoralis muscle this is consistent with pectoralis invasion.
   

FURTHER READING:
Radiologists’ Role in Breast Cancer Staging: Providing Key Information for Clinicians (RadioGraphics, 2014)