What Causes White, Circular, Oval White Patches In Neck And Upper Chest?

Hi doc! i have developed 3-4 white circular, oval white patches in neck and upper chest which are non-itchy since two months in this hot sweating summer season. My neck nas tanned due to sweat and have become dark. due to this, white discoloration is quite visible. could this be tinea versicolor? what treatments to be taken? will this white/light discoloration completely disappear?