A biopsy device and method are provided for obtaining a tissue sample, such as a breast tissue biopsy sample. The biopsy device includes a disposable probe assembly with an outer cannula having a distal piercing tip, a cutter lumen, and a cutter tube that rotates and translates past a side aperture in the outer cannula to sever a tissue sample. The biopsy device also includes a reusable handpiece with an integral motor and power source to make a convenient, untethered control for use with ultrasonic imaging. The reusable handpiece incorporates a probe oscillation mode to assist when inserting the distal piercing tip into tissue. The motor also actuates an attached tape indexing mechanism in coordination with movement of the cutter tube to provide sequentially stored tissue samples in a replaceable serial stacking assembly.