Mammogram showed a suspicious mass 8 mm x 8 mm. what's the next step?

Depends: Prior mammograms for comparison are critical. Also depends on whether this is a screening versus diagnostic mammogram. Likely you will need additional x-rays and/or ultrasound, possibly biopsy. This needs to be evaluated by a doctor.

Biopsy: We use a grading system to categorize abnormalities on mammography. "suspicious" means that it is a bi-rads 4 category, necessitating (nonsurgical) biopsy for definitive diagnosis. If this was seen on mammography and ultrasound, we usually guide the needle by ultrasound. While this is very anxiety-provoking, those abnormalities deemed "suspicious” are cancerous less than 30% of the time.

U/s then biopsy: If the mammogram is "suspicious", then a biopsy is indicated to establish a diagnosis. 80-85% will still end up benign. In almost all cases the sampling should be by needle (core) biopsy. In general, one shouldn't go to the or without a diagnosis. An u/s may see the lesion and guide the bx. If not, then a stereotactic bx can be done. All are office procedures best done by a breast surgeon.

Mass: Probably ultrasound, and if confirmed on ultrasound, the radiologist can perform an ultrasound guided core biopsy to establish a diagnosis. If not seen on ultrasound, a core biopsy can be performed by the radiologist with stereotactic guidance.

Biopsy: If you truly have a suspicious mass on mammogram, the next step should be a biopsy. Talk with your doctor about who should do this. Good luck!