How can I get rid of this brown rough mark in between my breasts?

likely this is PIH or acanthosis that needs skincare, peels and RX minocycline. I suggest seeing an expert.

this is post inflammatory hyperpigmentation/melasma/discoloration that needs cosmelan or enlighten peels at home which we can do virtually and send to your home along with aerify peels regularly, vivatia foam, restorsea 10x, faith essence serum, and cosmelan 2 cream.

Hyperpigmentation from any type needs a combination approach of peels like cosmelan, enlighten and aerify,  lasers like clear and brilliant and aerolase or laser genesis, radiofrequency like venus viva, and constant skin care and sun protection.  Bimonthly facials with silk peel dermalinfusion is essential to hydrate, exfoliate and infuse vitamins and antioxidants into the skin.  If you have acne you can do additional treatments and peels to get more improvement.  I suggest a formal consultation with an expert in lasers and peels. Best, Dr. Emer.