Suggest Remedy For Skin Discoloration

Hello,I have this skin discoloration that has been appearing on my neck for awhile now. It s size increases and decreases, as well as the how dark it becomes. At its darkest, it is almost a very light red, like a sunburn, at its lightest, its only noticeable to myself. It never itches, but there is a very slight noticeable difference in skin texture when I run my finger over the area. Its shape is patchy. Of course I ve pondered whether it could be something serious, but it doesn t seem to be problematic other than visual. I had a lot of problems with athletes foot while in the service, which at times got severe. Is it possible or likely this is fungal in nature? More than anything, I m just worried it isn t a major sign of a serious disease. Thanks!