BASED on the information its seems like "CHLOASMA" which are normally found in various body parts due to increase in estrogen
which stimulate the MELANIN
pigment over production.
No need to worry about it, getting into any form of cancer but its seems a cosmetic issue as far as I can understand. In such cosmetic issue the simple excision of the area will do the trick , but second issue is the healing may lead to formation of scar, hence need to consult a LASER
or cosmetic surgeon to deal with it.
1) Nothing to worry its normal occurrence in or after pregnancy
2) Consult a COSMETIC/LASER surgeon in case of its removal, as normal excision may lead to scarring.
Hope it helps to solve the issue.
Dr. JAY PATEL.