Inclusion Criteria:  Women who received a biopsy-confirmed diagnosis of a ER+ endometrial cancer, or; Women with a suspected ovarian cancer, or; Women with recurrent endometrial or ovarian cancer and with a ER+ primary tumor, and; Planned surgery, and; Stage 1A cancer and more, with primary more than 1 cm, and; Able to tolerate supine position, and; Written consent given by the patient.  Exclusion Criteria:  Pregnancy, or; Replacement hormone therapy concomitant to 4FMFES-PET, or; Use of estrogen-based oral contraceptives concomitant to 4FMFES-PET, or; Anti-tumor hormone therapy that compete with estrogen receptors concomitant to 4FMFES-PET, such as tamoxifen and fulvestrant. Withdrawal of such therapies 8 weeks prior to the 4FMFES-PET scan will enable the patient to the imaging test, or; Cirrhosis, acute or chronic hepatitis, or any other hepatic problem that might impede the normal elimination of the PET tracer, or; Hypersentivity to either FDG or 4FMFES, or any of their consittuants.