Had vacuum breast biopsy 3 months ago and area near biopsy site feels firm still. not rock hard but almost like a little lump. biopsy was benign breast tissue. what could be causing that firmness?

Post biopsy lump: Could be residual hematoma from the biopsy. Also scar formation or oil cyst formation/ fat necrosis. All of these are benign processes, but best to follow up with your doctor so he/she can assess the site

Hematoma: No matter what kind of biopsy is perfomed on the breast there is always the possibility of a small degree of bleeding locally. If an open biopsy is carried out, surgical closure to prevent even small spaces at the bx site from remaining. Without guaranteed control of any oozing into the biopsy site a hematoma and some hardening of the area can occur

Hematoma or inflamma: You may have a hematoma which is a bruise if the tissue from the biopsy and your body will re absorb it over time. It may also be an inflammatory reaction to the biopsy marker if one was placed. If you and your doctor remain concerned because the area is not softening over time, then your doc might consider an ultrasound