Why do we get fatty lumps?

Kat Arney put this to fellow Naked Scientist Chris Smith...

Chris - It sounds to me like these are what we call a lipoma or when you have more than one, they are lipomata which are benign tumours or benign growths of fat. They may also be fibromas because that's fibrous tissue, but they sound like the fatty equivalent - fibro and lipomas. There is a condition and it's called familial lipomatosis. It's very rare. About 0.002 per cent of people have this. It's caused by a gene which is usually a dominant gene - as you've just heard what that is from Kat - and that means you usually see this running in families. But because with every generation, you pass on 30 to 50 new genetic changes or mutations from parents to offspring, these changes can arise sometimes de novo. In other words, out of the blue. And so, there may be no obvious family connection because this is a new mutation. We don't know why it happens but we know it's twice as common in men as women. It tends to occur on the trunk or on the limbs. It tends to spare the shoulders and the head. It is not harmful really and most of the time, these things, despite being a bit unsightly, won't do you harm, they can be shelled out or removed. But because they are growing from a preponderance of the fat cells to form these little benign tumours or growths, they do recur. And so, just because you take one out, you may get another one somewhere else.