Dear Prabhakar,

I guess it is difficult to find ultrasound image database for breasts. However, you may find a Digital Database for Screening Mammography (DDSM) for breast cancer in the following site:

http://marathon.csee.usf.edu/Mammography/Database.html

You can try this

http://marathon.csee.usf.edu/Mammography/Database.html

I do not think I have seen database for  Breast Ultrasound Images but in radiology , you can find  The mini-MIAS database of mammograms in this site:

http://peipa.essex.ac.uk/info/mias.html

There is no database for breast  USG as far as I know. May be it is time to create such a base? It would be interesting for comparison in between different methods of breast cancer classification.

there is a good database with ground truth provided by SIIT biomedical unit , Thammasat university, Thailand 

http://onlinemedicalimages.com/index.php/en/

The authors of the following article have kindly provided open-access breast ultrasound radiofrequency data, together with outlined tumor boundaries: Piotrzkowska‐Wróblewska, H., Dobruch‐Sobczak, K., Byra, M., & Nowicki, A. (2017). Open access database of raw ultrasonic signals acquired from malignant and benign breast lesions. Medical Physics, 44(11), 6105-6109. Please refer to the article for the way to downloading the data.