I Was Just Diagnosed With A 3.5cm "maternal Side Placental

I was just diagnosed with a 3.5cm "maternal side placental tumor". My OB originally thought it was a chorioangioma due to its vascularity, however, there is no vascularity WITHIN the tumor itself, only around it.

My MFM doctor kept referring to it as a "tumor" that we would need to watch and see what happened but I don't feel satisfied with that answer. Is it benign? malignant? harmful to me or the baby? I'm still worried.

Do any of you have any ideas of what it may be?