The Ultrasound was done due to post menopausal bleeding.
I started HRT at 49 when my estrogen level was 28 and I had only had 3 periods over the prior year. Once I initiated the HRT I began getting my period again, though much lighter than when I was younger. Had a transvaginal ultrasound that found no issues. Continued to have the period/spotting and had another TVUS at 54 with no issues found. About a year and half later noticed the bleeding was heavier and coming more ofter, though still cyclical - almost as if I was still in peri and had irregular periods. Went to gyno and had another TVUS. This time it showed the complex cyst.
I have never had an abnormal pap, don't have endometriosis, and have had no fibroids.