18 female. 1/2 mm mole on abdomen. light brown with some dark brown spots. fairly new. elevation decreased a little. concerning?

Best to see your Dr.: It is impossible to know for sure without seeing you and your mole in person. The odds of an individual mole becoming cancerous is less than 1 in 3000 but the risk for an atypical mole is about 1 in 100 and this sounds atypical due to the dark spots. Best to err on the side of caution and see a Dr. See https://www.skincancer.org/skin-cancer-information/atypical-moles/warning-signs-and-images