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Asymmetrical density in mammography

Asymmetrical mammographic density is a mammographic morphological descriptor. It is given when a there is increased density in one of the breast on one or both standard mammographic views but without evidence of a discrete mass. An asymmetrical density can be further characterised as:

Pathology

Asymmetrical can arise from both benign and malignant causes:

Benign causes
 Malignant causes

The mammogram and asymmetry

In practice, an asymmetry which is stable and unchanged over years does not deserve attention. An asymmetry is usually seen on both views of the breast if it is not a summation shadow. Typically, summation shadows are seen on one view only and disappear when the view is repeated or a rolled CC of ML view of the breast is done. Ultrasound is not needed if you are working up a summation shadow.

Of more significance is a developing asymmetrical density. Remember, not all carcinomas present in imaging as a mass, some develop and present as asymmetry only with no noticeable mass. A developing asymmetry deserves your full attention and justifies workup. It is rarely helpful to make magnification views of an asymmetrical density, if you enlarge a blob you tend to get a bigger blob so you rarely get extra information to help you decide what you are dealing with. Its often more useful to do rolled CC and ML views of the breast and compare with the original mammogram. If the lesion was a summation shadow, it is not seen on the additional views. If it persists, it is a significant finding and ultrasound is indicated.

Work up

Before you recall an asymmetry, go through the old images and decide whether the density is actually changing over time. In general, malignancies grow over time and benign lesions remain stable. 

A parenchymal distortion with a dark centre is a Birads IV lesion. A parenchymal distortion with a white centre is a Birads V lesion.

Additional imaging may include:

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