I have a black spot on my spine on my back what can it be?

Pigmentation : Miles can develop and become very dark and should be evaluated by a dermatologist

What is the shape: Usually spots that are symmetrical are begign round spot you can draw a line down the middle and it's equal on both sides however if you can't see it have a doc check if it is bleeding or growing or changing doesn't treat it is cancerous but a deem should look at it