Polo Ralph Lauren Jacket Quilted Bomber Insulated Navy Blue Youth XL (18-20)

Polo Ralph Lauren Jacket Quilted Bomber Insulated Navy Blue Youth XL (18-20) Should fit a men's small too if necessary. There is a fairly large area of discoloration at upper back area, no idea what it could be. I'd soak it in oxiclean but I'd worry about the red lining shedding it's dye all over, so selling it as is. Possibly a grease stain?. It doesn't stick out at all in normal light. Also a small loose thread at back left armpit area. otherwise excellent condition