Hi and welcome to HCM.
It doesnt seems to me like it will be malignant. Usually bone metastasis
is well seen and radiologist
easily verify this. Also, it is unlikely that ovarian cancer
would meatstise after 25 years. This bone lesion can be caused by degenerative changes or osteoporosis. Pain would be caused by this as well. If you want to be sure I suggest to do tumour markers and bone scintigraphy
. This would make everything clear WIsh you good health.