Uterine leiomyomata and endometrial proliferation in postmenopausal women treated with the anti-oestrogen tamoxifen.

Two cases of fibroid growth and endometrial proliferation in postmenopausal women on tamoxifen (anti-oestrogen) therapy for breast cancer are described. Oestrogen in association with growth factors may control fibroid growth and differentiation. The possible mechanisms and consequences of tamoxifen-induced fibroid growth are discussed. Oestrogen responsive tissues demonstrate a differential and contrasting response to tamoxifen and caution should be exercised in the expansion of its clinical application. Women on long-term tamoxifen therapy may benefit from ultrasound surveillance of their uterus and endometrium, with biopsy in suspicious cases, as there is a paucity of data on malignant transformation of these benign lesions induced by tamoxifen therapy.