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MEDICINE 101

THE MAMMOGRAM

If you're a woman over 50, you're probably familiar with mammograms & maybe even more familiar then you'd like to be.  There's the squeezing pain & the uncomfortable position.  It's not an easy test but what's the benefit of all that discomfort?

A mammogram is simply an X-ray of the soft tissues of the breast.  As the X-rays pass through the breast they are absorbed differently by the structures inside the breast and this is what makes the pattern of the X-ray picture.   Think of the anatomy of the breast in terms of this cluster of grapes.   The breast has small circular glands that look like these grapes.  They produce and secrete milk, gathering it along these tubules to be expressed through the nipple.

A mammogram looks like this with the pictures of the two breasts set side by side for comparison.   The X-ray specialist reads the mammogram by comparing the structures seen on either side.

Here's a normal mammogram.   You can see the pattern of small grape-like clusters of glands and the tubing quite clearly.

Some breasts have much more fat in them than others.    Fat absorbs more X-rays and so the mammograms appear whiter & like this.

No woman wants to find a lump in her breast but often it's just a harmless cyst like this. A cyst is simply a cavity filled with fluid.   What happens is one of these grape-like glands gets blocked and then swells with milk-like fluid.  The cyst is usually fairly round, even and consistent in density.   

But of course in mammograms we're not looking for normal breast tissue or common cysts & we're looking for cancer.   We know that in cancer, cells are dividing quite rapidly so they end up being very hard and very dense collections of tissue.   They absorb more of the x-rays and end up looking white.  Because cancer is irregular, the edges of the cancer will look like this.  Also, only cancers produce a fine pattern of calcium that's deposited in the mammogram.  You can see it here. Calcium can be seen within the wall of blood vessels inside the breast or sometimes in benign patterns, but the presence of calcification is important because we see it in alot in malignant cancers.

The radiologist is looking for all these things after you leave the clinic, trying to pick up the slightest change or inconsistency.  But mammograms aren't perfect they can miss a cancer and they can misdiagnose a benign or harmles swelling.  But so far they're the best screening test that we've got.