Subjects will undergo a baseline QT scan, and a follow-up QT scan performed between 90 days and 180 days from their baseline QT Scan accompanied by a HHUS and ultrasound-guided breast biopsy following the first follow-up QT scan. BI-RADS will be confirmed by the radiologist at the time of the first HHUS. Subjects will receive a telephone follow-up contact approximately 2-3 business days after their ultrasound-guided breast biopsy to assess if any adverse events have occurred. Subjects will be asked to come back for an additional follow-up QT Scan 12 months from the time of their baseline QT Scan.

Subjects that have not had (2) two QT Scans before their breast biopsy and who haven't yet had a breast biopsy will undergo an optional baseline QT scan accompanied by a HHUS and ultrasound-guided breast biopsy. BI-RADS will be confirmed by the radiologist. Subjects will receive a telephone follow-up contact approximately 2-3 business days after their ultrasound-guided breast biopsy to assess if any adverse events have occurred. Subjects will be asked to come back for a follow-up QT Scan between 90 and 180 days from the time of their study biopsy.

Subjects that have had a breast biopsy on their identified breast mass(es) prior to study enrollment and have not already had two (2) QT Scans will undergo an optional baseline QT scan if between 0 and 30 days from their breast biopsy.

Subjects will be asked to come back for a follow-up QT Scan 12 months from the time of their study biopsy.

All subjects will be asked to agree to an ultrasound-guided breast needle biopsy by a qualified radiologist experienced in this procedure if not already completed prior to study entry.

The change in calculated mass doubling time using Quantitative Transmission Ultrasound (QT Ultrasound) from a minimum of two study timepoints will be measured and compared to mass histology.