Mucinous Carcinoma on Mammography

IMAGING FINDINGS: ​
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Standard Craniocaudal (CC) and Mediolateral Oblique (MLO) views of the right breast demonstrate an isodense, oval mass in the lower inner quadrant. The mass has primarily circumscribed margins, but is a new finding compared to prior exams.
 
WHY IT MATTERS:

1. Not all circumscribed masses on mammography are benign. Most will be either a cyst or fibroadenoma, but mucinous carcinoma is one of a few types of malignancy that can present as a relatively benign appearing mass on screening mammography. This case shows a new solid mass in a fifty year old patient, biopsy is always required, despite the relatively benign appearance.
   
2. Mucinous carcinoma is a subtype of invasive ductal carcinoma. It often has circumscribed margins and is T2 bright on breast MRI.
   

FURTHER READING:
​Mucinous Carcinoma of the Breast: MRI Features of Pure and Mixed Forms with Histopathologic Correlation (AJR 2009)