Go visit the link in Rooster's answer. It's very interesting even though it says the cause is unknown.
Mrs Didge would disagree. She insists that they're caused by QMS.
I have two lipomas. One is normal sized -- a couple of centimetres across -- on the side of my head. If I still had hair it wouldn't really be noticeable.
The second is enormous, as lipomas go. It's on my upper back and is a bout 10 cm (4 inches) across and 2 or 3 cm high. That's how Mrs D. Came to make her diagnosis. She says that QMS is Quasi Modo Syndrome/
