This study was performed to evaluate sonographic measurements of endometrial thickness in postmenopausal breast cancer patients being treated with tamoxifen and to correlate endometrial thickness with pathology, symptoms, and duration of tamoxifen treatment.

Pelvic sonograms and medical records of 91 postmenopausal breast cancer patients being treated with tamoxifen were retrospectively reviewed. Histologic results were available in 46 patients (51%). Endometrial thickness was measured in anteroposterior dimension and was considered normal when less than 8 mm. Endometrial thickness was then correlated with histopathologic findings, symptoms, and duration of tamoxifen treatment.

Forty-seven examinations (52%) showed endometrial thickness of less than 8 mm and 44 examinations (48%) showed endometrial thickness of 8 mm or more. Endometrial biopsy was performed in 10 women (21%) in whom the endometrial thickness was less than 8 mm, revealing seven normal endometria, one endometrial polyp, and two insufficient samples. Endometrial biopsy was performed in 36 women (82%) in whom endometrial thickness was 8 mm or more, revealing three cases with more than one diagnosis. In this group, diagnoses included 14 normal endometria, 12 endometrial polyps, four endocervical polyps, three hyperplasias, two endometrial cancers, one papillary syncytial metaplasia, one cystic change, one inflammatory debris, and one insufficient sample. Postmenopausal bleeding prompted 20 studies, 12 of which revealed endometrial thickness of 8 mm or more. We found no difference in endometrial thickness of patients who had bleeding versus those who had no bleeding. Endometrial thickness increased with the duration of tamoxifen treatment. Seventy-three women being treated with tamoxifen for less than 5 years had a median endometrial thickness of 5 mm, and 44% of biopsies yielded abnormal results. Eighteen women receiving tamoxifen 5 years or longer had a median endometrial thickness of 14 mm, and 58% of endometrial biopsies in this group were abnormal. The two endometrial cancers occurred in women who were treated with tamoxifen for 6 years. Correlation between duration of tamoxifen use and endometrial thickness was significant (p < .026).

The majority of women being treated with tamoxifen were asymptomatic, but 48% of sonograms revealed an endometrial thickness of 8 mm or more. Endometrial polyps, the most common abnormality, were diagnosed in 33% of biopsies performed for endometrial thickness of 8 mm or more. Endometrial thickness showed no correlation with symptoms, but we found a statistically significant correlation between increased endometrial thickness and duration of tamoxifen treatment that was longer than 5 years.