Small, brown lump on chest area? it seems to be going away, but i'm curious. it's moveable, and not tender.

The most common: brown skin lesion is a seborrheic keratosis...a benign lesion which appears to be "stuck on" the skin. If it is more like a lump it is likely a different benign growth...a dermatofibroma. It probably represents a fibrous or scar like reaction to minor trauma/insect bites. Flatter brown spots are nevi/moles, and, as you know there are dangerous ones..melanoma skin cancer. If ?'s, have Doc check:)