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Shadowing on breast ultrasound



I developed a cyst in my left breast recently that was seen on breast u/s but not on my mammogram. ( the mammogram report said I had dense breasts ). But also seen on the breast u/s was an area of shadowing that made my dr. suspicious. He rescanned me about 10 days later and the cyst was gone but the area of shadowing persists. He wanted me to come back in a month and have another u/s and if the shadowing persists, then do a biopsy then. His theory being if it was associated with the cyst, it would go away. I asked him if he thought this could be a malignancy and he said he didn`t know. I am not comfortable waiting a month and asked if he would consider doing the bx sooner. His nurse told me no – they would not do it any sooner and that a month is not going to make any difference if it is a malignancy. I have made an appt with another surgeon for a 2nd opinion. My question is: 1. what causes shadowing 2. if it truly is associated with the cyst, shouldn`t it be gone also since the cyst is gone. On the u/s screen, the area of shadowing looked like a large inverted V.I know you cannot make a diagnosis,just wanted to know ,in your experience, what shadowing means. Thanks for your help.


Cysts are benign fluid-filled structures in the breast.  They do not cause shadowing on ultrasound.  Marginal shadowing – black shadows off both edges of a mass – is also a benign finding (can be seen with benign fibroadenomas).  Posterior shadowing – black shadows off the middle of a mass – is concerning for cancer.  I would seek a second opinion.  If the ultrasound is being done correctly, then you need a biopsy.  It is true that waiting a month won’t affect your health, even if you have cancer.  The wait is mentally difficult, however.

For more information:

Go to the Breast Cancer health topic.