Unusual ultrasonographic appearance of the uterus in patients receiving tamoxifen

Abstract

Tamoxifen is widely used as adjunctive therapy for patients with breast cancer and has been suggested as protection against the development of breast cancer in women at risk on the basis of heredity. It is a nonsteroidal estrogen antagonist, but like all antagonists it has some agonistic properties. Its administration should result in atrophic changes in the endometrium, but paradoxically some reports have found hyperplasia and even carcinomas developing prospectively in patients on tamoxifen therapy. Increasingly, endovaginal ultrasonography is being used for endometrial assessment in a wide variety of patients. This report is the first description of an unusual ultrasonographic finding in the uteri of some patients receiving tamoxifen. Initially believed to be endometrial in location, when viewed after fluid instillation (sonohysterogram) the heterogenous bizarre ultrasonographic appearance was actually found to represent small subendometrial sonolucencies in the proximal myometrium. Because none of these patients were clinically bleeding and all had inactive endometria on biopsy, it seems prudent not to overinterpret ultrasonography findings in patients receiving tamoxifen who have not had fluid-enhanced assessment.