How soon after development do most people notice or find out they have breast cancer?

Varies: from person to person. Those persons who regularly examine their own breasts ( BSE) and go for routine, age indicated mamograms are more likely to be diagnosed sooner.

5-20 years: The smallest tumor detectable by a mammogram is 0.2 mm. Cancer starts as a single cell which divides repeatedly. The growth rate(doubling time) of individual breast cancers varies from 80-200 days(time to double in size). THE AVERAGE WOMENS BREST CANCER HAS BEEN GROWING FOR 12-15 YEARS BEFORE IT IS DETECTED BY MAMMOGRAPHY !! An aggressive cancer may take 5-7 years before it is detected by X-ray

Method for dx: Depending on how one makes the dx of breast Ca the interval to dx varies. If one relies on mammo, a lesion can be detected as microCa . A bx at the time may indicate DCIS with no invasion . A mammo may dx a small stellate lesion growing for several months but is still not palpable. If one waits to bx the first palpable lesion at about 1-2cm. this lesion may have been growing for 1-2 yrs .