Figure 5b. False-positive US appearance due to endometrial cystic atrophy in a 71-year-old woman. (a) Sagittal transvaginal US image demonstrates a retroverted uterus with a thickened heterogeneous endometrial echo complex (calipers) and small cystic spaces. The endometrial thickness measurement is 14 mm. F = fibroid. (b) Sagittal hysterosonogram shows fluid (*) in the endometrial cavity, which has a lobulated outline with scattered protuberances (arrows) that are indistinguishable from focal areas of endometrial thickening. Correlative hysteroscopy and histopathologic analysis revealed "tamoxifen mucosa," cystic atrophy, and dilated glands, with no evidence of endometrial hyperplasia or carcinoma. F = fibroid.