You have not given the proper history . more over age is not clear .if she is post menopausal ,get the screening for ca .if they suspect uterine cancer ,there will be h/o bleeding per vagina .to rule out she should undergo diagnostic hysteroscopy . instead of MRI she should go for laparotomy , after all the investigations .&toumer markers.
Next Steps
get one more scan done .if all the investigations are normal a course or antibiotics will do .