During sonographic examinations using the new color Doppler technique, maximum-entropy method (MEM), it was discovered, by chance, that artefacts which are produced by vibrations of the thorax can be used to differentiate between malignant and benign breast lesions. These artefacts, in the form of small color pixels, can either be brought about by vocal fremitus known from internal medicine or by humming in a low tone.
In the case of malignant tumors, the color pixels are visible in the middle of the sonographically portrayed tumor as well as in the surrounding tissue, whereas in benign tumors the artefacts are only found in the surrounding tissue and are quite clearly not present in the center of the tumor.
On the preoperative day, 95 patients with 46 benign and 49 malignant lesions were examined using the method described above. In 91% the differential diagnosis was in accordance with the histological results. In seven cases a benign lesion was classified before the operation as malignant and in two cases malignancy was incorrectly diagnosed as benign.
Our explanation of the phenomenon is based on the fact that most benign tumors exhibit a restricted growth and form a clear-cut boundary with the surrounding tissue, so the vibrations are not conducted into the tumor. In contrast, malignant lesions grow by infiltrating the surrounding tissue, allowing the vibrations to be conducted into the tumor, where they can be demonstrated as small color pixels. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology