A PET/CT scan will answer the question for you whether it is a cyst or benign or malignant.
MRI may or may not tell it is ovarian cancer or not; and the PET/CT scan also can tell you whether the recurrence is hot or not.
Below is a copied message about PET/CT scan usage from the experience forum under radiation.
"I will recommend PET scan right after CAT or MRI if recurrence is confirmed or small lesions detected by MRI but not sure whether they are cancerous or not.This will give the doctor more info about the lesion such as whether the lesion has metastasized or give the doctor a more informed idea what he/she saw on the M R I or CAT scan indeed is a tumor that has metabolic activity(maxSUV) value and required immediate attention such as chemo therapy or resection,RFA,chemoembolization,radioembrolization,PDT,SBRT .
By doing so,the doctors will not be confused with and discard the lesion as being part of the artery or hepatic vein or other forms of lesions and ask the patient to return in 3 months to repeat the scans to make sure.As you all know, 3months is a lot of valuable time for patients as well as caregivers. Who wants to wait for another three months? I think this is the part of early detection that we,ourselves, can monitor and provide the early benefit of more treatment options to the patient.
PET can find or confirm cancer metastasized activities in the other parts of the body.PET may not be a good choice to locate NEARBY metastasized cancer activity such as the lymph nodes that are very close to the primary site of CC because the closest distances between the lymph nodes and the CC.)
PET Scan allows visualization of CC because of the high glucose uptake(SUV) of the bile duct epithelium(the lining )-- the "Hot spots" will light up on the PET scan and show the relative cancer activity of the lesion by the SUVmax value."
Please know that my personal opinion is not intended nor implied to be a substitute for professional medical advice. If provided, information are for educational purposes.Consult doctor is a MUST for changing of treatment plans.