Is a heterogeneous breast mass with posterior attenuation suspicious of malignancy? i have very cystic breasts so us was not that clear.

Need all info: Give us some more details. Have you had a physical examination by your doctor? He/she can guide you further based on whether there is a palpable lump in the breast or not? If there is lump which can be localized easily a Needle biopsy should be a serious consideration. A comparison with previous Mammograms/Ultrasound examination will be most helpful to determine any recent change.?

Generally,: the ultrasound descriptors you mention imply a more suspicious nature. However, all of the imaging and clinical features must be taken into account. Also, keep in mind that "suspicious" in breast imaging implies a chance of malignancy between 2%-95%, which is a huge range, and in fact 75% or so biopsies of suspicious masses turn out benign.