How to treat Congenital and Dermal Pigmentation for FP 3-4?

I have mostly olive/fair skin, but have large areas of deep almost black pigmentation (debilitating). Dermatologist said it's Acanathosis Nigricans, but Blood Tests detect no metabolic syndromes. Anyways, tried HQ 2% by Vivier, Differin Adapalene, Vitamin C and Azelaic Acid 10%. It worked on the PIH and Acne but not on the deep pigmentation, any lasers, surgery, peels or treatments that are effective? (Advised to not get CO2) I don't mind expense treatments, as long as effective. (No obagi pls)