Oval tan skin lesion with dark crust center

I have had this "Tan Oval shaped 1 inch raised skin with a dark crusty center lesion" for 5 years now. It has progressively grown at a slow pace. This year I have 9 more also growing at a very slow pace. They start out as a tan discoloration on my back and as it gets larger (always oval in shape) the center turns dark, crusts over and falls out/off much like a scab. Leaving a pinkish flaky center of skin underneath. Then it happens all over again. This process doesn't start happening until they are about 1/4 inch in size. In 2005 I had surgery and (it was much smaller then, maybe a 1/2 inch) the surgeon casually said "it was nothing"...then in 2008 I asked my Primary MD and she too, said: "it was nothing"...OK. so I guess they are nothing but it would be nice to get rid of this "nothing"...anyone ever heard or experienced such a thing and if so, did it ever go away. They are not painful, just gross and reproducing. Any ideas!