I have a large brown splotch on the area beneath both my breasts. it lays vertically on my solar plexus. it's not tineas versicolor. it doesn't match ?

How long: How long has this large brown splotch been present beneath your breasts? Some areas of hyperpigmentation can be congenital. Chronic skin irritation such as with fungal infections which are common if the area beneath your breasts stay moist can also cause the skin to be hyperpigmented. An exam is necessary to know for sure what is going on. Hope this helps.