Biopsy device with variable side aperture

A biopsy device and method are provided for obtaining a tissue sample, such as a breast tissue biopsy sample. The biopsy device may include an outer cannula having a distal piercing tip, a cutter lumen, a side tissue port communicating with the cutter lumen, and at least one fluid passageway disposed distally of the side tissue port. The inner cutter may be advanced in the cutter lumen past the side tissue port to sever a tissue sample. After the tissue sample is severed, and before the inner cutter is retracted proximally of the side tissue port, the cutter may be used to alternately cover and uncover the fluid passageway disposed distally of the side tissue.