Ask an Expert: Breast cancer growth rate

Q: How long does it take for breast cancer to grow? My doctor just examined my breasts a month ago (no lumps), and today I found a lump. Is it possible that breast cancer could have developed so quickly?

Answer from the expert staff of breast cancer research at the Robert W. Franz Cancer Research Center at Providence Portland Medical Center:

Like a lot of cancers, breast cancer grows by simple cell division. It begins as one malignant cell, which then divides and becomes two bad cells, which divide again and become four bad cells, and so on. Breast cancer has to divide 30 times before it can be felt. Up to the 28th cell division, neither you nor your doctor can detect it by hand.

With most breast cancers, each division takes one to two months, so by the time you can feel a cancerous lump, the cancer has been in your body for two to five years. It can certainly seem like a lump appeared out of nowhere – especially if you or your doctor have recently examined your breasts and not felt anything suspicious – but in reality, the cancer has simply doubled that one last time necessary to be noticeable. By the time you can feel it, a breast tumor is usually a little more than one-half inch in size – about a third the size of a golf ball. It has also been in your body long enough to have had a chance to spread.

This sounds scary, but what it really underscores is the importance of regular mammograms. These screening tests can usually detect breast cancer when it’s about one-quarter inch in size or smaller – a year or more before it would be detectable by hand. Mammograms also make possible the early diagnosis of some pre-cancerous conditions and early-stage cancers that appear as tiny calcifications (microcalcifications) on mammography, but aren’t detectable by physical examination.

It’s important to realize that there are two types of mammograms:

A screening mammogram is performed in cases where there isn’t any known problem. This type of mammogram is used for annual exams.
A diagnostic mammogram is performed when there is a known problem that requires careful evaluation. Diagnostic mammograms provide much more extensive images than screening mammograms, such as views from additional angles and compression, or blow-up, views. Often an ultrasound will be done in addition to the mammogram if there is a palpable lump. Make sure you receive a diagnostic mammogram if you’ve found a lump.

Once a breast cancer gets big, every doubling is significant. If you find a lump, see your doctor as soon as possible. Don’t settle for just a mammogram if the mammogram doesn’t find anything. The next step should be a screening ultrasound, and if those results are indeterminate you need to get a biopsy. Ask you doctor for these tests if he or she doesn’t schedule them.

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