Final answer:
Postmenopausal bleeding should be considered endometrial cancer until proven otherwise, due to the changes in hormone levels during peri-menopause which might lead to endometrial hyperplasia and an increased cancer risk.
Step-by-step explanation:
Postmenopausal bleeding is endometrial cancer until proven otherwise. During the menopausal transition, known as peri-menopause, the levels of estrogen may still be similar to pre-menopausal levels, but the level of progesterone from the corpus luteum is reduced, leading to potential abnormal endometrial hyperplasia. While some conditions like uterine fibroids and irregular bleeding are benign, the potential link between prolonged unopposed estrogen exposure and endometrial hyperplasia increases the concern for endometrial cancer, thus making it a priority to rule out this serious condition when postmenopausal bleeding occurs.