I don't think i am asking question right if my ovary is enlarged would it be due to a mass or can ovarian cancer cause ovary to swell with no mass?

No difference: An enlarged ovary, depending on how enlarged, may or may not have a detectable mass, yet still harbor cancer. If the ovary is enlarged, with or without an obvious mass, the matter needs to be investigated by your doctor.

Definitions: A mass usually describes an abnormal enlargement that could be solid or cystic sometimes similarly referred to as a tumor. Masses or tumors can occur in any organ or the body like the ovary but they can be benign or malignant. It is then called cancer if it is malignant as shown on a biopsy. Thus, the cause of a mass may be a cancer or a benign condition.