Is a 3 cm solid, sperical, dark spot on an ovary something to be concerned about? what promps investigation? growth rate? thanks.

Maybe: Solid tumors of the ovary are the most concerning type. What did you doctor say? Sometimes, at that size, the doctor will repeat the ultrasound in 6-8 weeks to see if it changes in size. Sometimes they will order a ca-125 alongside. They should take a family history to make sure no breast, uterine, ovarian, or colon cancer in your family. See your doctor for answers as they know your history.