Why is it that every single organ and component of the human body gets cancer except the heart? I have heard about cancer of everything from the brain to the blood; it seems no appendage is safe from the ravages of the big C. Yet I have never heard of anyone getting heart cancer. Am I merely medically ignorant or does the big love muscle have a secret weapon?
Peter Scott, Burbank, California
We’ll get to the big love muscle next week, Peter. For now let’s stick to the heart. Cardiac tumors are rare, but they do occur, usually when cancer spreads from some other part of the body. These so-called metastatic tumors are 20 to 40 times more common than primary tumors — that is, cancers that start in the heart. Of the handful of primary tumors, two-thirds, such as your myxomas and rhabdomyomas, are benign, at least in the sense that they won’t spread and destroy the heart all by themselves. However, they can block blood flow or cause arrhythmias or other abnormalities, so when a tumor is discovered the standard procedure is to cut the thing out, benign or not.
The heart isn’t alone in being relatively immune to primary tumors. Muscle cancers in general (the heart is basically a muscle) are fairly rare. Nobody knows for sure why this is so, but one plausible guess is that it has to do with the rate at which cells are replaced. The most common types of cancer are adenocarcinomas, i.e., cancers of the glands, glands being the parts of the body that secrete something. Glandular cells tend to have a higher turnover than other types of cells and for that reason are more prone to cancer, since it’s thought a mistake in cell replication is what causes a tumor to start (I’m also tempted to say glandular cells are more exposed to carcinogens in the environment, but the Science Advisory Board tells me this would be a rash oversimplification.) Muscle-cell turnover is much less than that of glandular cells, so cancer has less chance to get started.
Still, cancer of the heart can happen in a big way on occasion. Doctors once removed a 4,800-gram cardiac tumor — more than 10 pounds — from a patient. If you’ve got a heart as big as the great outdoors, you might want to have it checked out.
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