Hi I have a slightly dark brownish pigmentation of only one of my breast. It is around the lower fold, hasn't changed color or consistency, seems like lines and dots, doesn't itch or pain. I m 25, Indian subcontinent region, healthy, no previous health histories other than appendectomy. It is not acanthosis nigricans or PCOS related. Doesn't seem like a fungal or any infection. It as been there for about a month now. No trauma to the region as well.

Summarized question: Dark brownish pigmentation on lower breast fold. Not acanthosis nigricans, PCOS related. What is it?