My personal view is that fremitus is not looking for flow. It is looking for artifact caused by tissue vibration. If a lesion is benign it sits in the breast architecture and simply displaces tissue around it without actually invading the tissue. Hence it is not “locked into” the tissue around it. When you perform vocal fremitus testing the benign lesion will not vibrate as much as it is not locked into the surrounding tissue. In the case of a cancer the mass has spiculations travelling through and invading the adjacent breast tissue and hence it is “locked into” the surrounding tissues and vibrated in synch with them causing the Doppler artifact.
So no Doppler signal suggests a benign process and filling of the lesion with Doppler signal suggests a malignant process.
In either case we are not assessing real flow but rather looking at artifact caused by tissue vibration. Flow is best assessed using Superb Microvascular Imaging (SMI) or if you don’t have this technology try Advanced Dynamic Flow (ADF)