So, many years ago, I had a breast cancer scare. And BOY, was I scared. It was actually my very first mammogram. I got a call that I got a BiRad of 5! With microcalcifications that met multiple criteria for concern (number, shapes, edges, etc.). The Bi Rad scale is 0 to 6 and the radiologist rates an 'abnormal' mammogram on that scale. 0 is likely not cancer at all and 6 is almost definite cancer. Needless to say, that 5 scared the poop out of me. I went to a specialist within days of the results. I had a needle biopsy. And waited. I did not have cancer. So, I tell you this because that is very often the case. Mammograms are highly sensitive and flag things. We have follow up to make sure we're okay. That covers your left breast. Get the needle biopsy. And know that it very well could be fine.
Right breast. A hypoehoic mass means it is dense. It does not always mean something is wrong. The mass is more solid than usual and needs investigation. Did they assign a Birad score to this for you? Really, hypoechoic means it is solid and not liquid. It's a lesion or mass and NOT a cyst. That's all it can mean. The percentage is that only .04 percent of these findings turn out malignant. Keep that in mind.
But you have to find out. Let me know the results of your follow up.