Hi recently i had a mri scan of my spine for lower back pain which found a 6.7 cm cyst on my ovary. is this likely to be cancer? i am very worried. i have pcos. 25 year old female?

Ovarian cysts are sacs in the ovary filled with fluid. Follicular cysts occur when an egg follicle fails to open and release the egg during a menstrual cycle. Simple ovarian cysts are common, harmless, will disappear within a few months, and usually not a sign of impending cancer. Rupture may cause pain and bloating. Follow-up with physician is important.

Sounds like imaging has confirmed an ovarian cyst which may or may not be responsible for your back pain. Have your gynecologist assess this and decide management.