Dark spot in sinus cavity on MRI

Past 3 weeks I've been having dizziness, headaches, slight runny nose and mucus in the forehead. I went to a neurologist and had a head MRI done. Everything was fine except a dark spot in forehead sinus cavity. What could this be? Could it be a polyp or cyst? Is sinus cancer rare?
Source: MD Health Forum - Medical Discussion Boards - Category: Consumer Health Advice Authors: Tags: Ear, Nose and Throat Source Type: forums