Slow Growing Developing Asymmetry on Mammography

IMAGING FINDINGS: ​

​Serial mammograms of the right breast over five years. There is a developing asymmetry in the right breast. Notice the gradual increase in density in the upper outer right breast without an obvious mass. It is difficult to appreciate an abnormality on any given year, however comparison with multiple prior studies reveals a definite change.

WHY IT MATTERS:

1. Developing asymmetries are relatively rare but very concerning imaging findings on a mammogram.  They can be very subtle. Identification of the focally increasing density highlights the importance of having and looking at multiple prior exams.
2. This case turned out to be an invasive lobular carcinoma (ILC). ILC’s grow in a sheet-like fashion, insinuating through the breast parenchyma.  They often will present as a gradual developing asymmetry.

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FURTHER READING:
The Developing Asymmetry: Revisiting a Perceptual and Diagnostic Challenge (RSNA 2015)