Anytime we develop a new growth or discoloration on the skin, it should be evaluated by a a qualified physician. This is the type of problem that you can first bring up with your primary care physician
who may choose to refer you to a dermatologist
. Spots on the skin have many possible causes ranging from simple benign nevi (such as a birth mark), to simple fungal infections, rashes, and skin cancers. In this case, it sounds like your patch of discolored skin is actually growing on you stomach. Most patches of discoloration, especially if they are not raised off the skin, turn out to be a skin fungal infection known as tinea versicolor. This is a benign infection that can be treated with topical or oral anti-fungal medications. On the other hand, growing discolorations can also be more worrisome things such as melanoma, a cancer of the skin. For this reason, you never want to let a skin problem go without it being evaluated. I suggest you bring up this problem with you primary care physician. I would schedule the appointment as soon as possible. He or she may be able to quickly diagnose it, or refer you to a dermatologist for further evaluation and if necessary, treatment.