Ovarian cancer detected. Before surgery!

Hi, My mother had a severe abdomen pain due to which we admitted to hospital and did few scans. The scans showed a 12cm cyst on left ovary and 3cm cyst on right ovary. Doctor suggested immediate removal of cysts along with ovary. But during operation, the surgeon felt the uterus dint look healthy and did a total hysterectomy. The parts were sent for biopsy & the biopsy report said it was invasive carcinoma-serous adenocarcinoma, low grade with capsule intact and lymphovascular invasion seen.We got a abdomen and pelvis CT scan done and report looks normal. Now one oncologist says we have to get a ometectomy immediately which again after biopsy if abnormal, should be followed by chemos. V took a second opinion from another oncologist who says they will monitor the patient by doing a CT125 every 2months for few months and see the count. If count is normal, no treatment else they should do omentectomy and few chemos. Please advise as to who is going in right path. CA125 before surgery