When you receive a letter from a mammography 20 days later saying they saw an abnormality, does this mean its cncer? what can it be?

Need more: Imaging. Sometimes things are seen on a screening mammogram that need to be further evaluated. You will get a diagnostic mammogram with more pictures and compression images to better see the area in question. Often a breast ultrasound will be performed. See mammogram at radiologyinfo.Org and womenshealth.Gov. Too soon to know if there is any cancer present.

Maybe/maybe not: Mammography screening ; interpretation is set up to be very conservative -accepting false positives so not to miss cancer. 80-85% of mags recommended for bx end up benign. Many screening finding are resolved w/add views. Depending on positioning and compression tissue can fold or superimpose ; look like a mass. Get f/u imaging as advised +/- see a breast surgeon for further opinion.

No, it doesn't: mean there is cancer. Suspicious mammographic abnormalities turn out to be benign about 80% of the time.