[Expansive uterine myoma during tamoxifen therapy. 11 cases].

Tamoxifen, a non-steroid anti-oestrogen derivative of diethylstilboestrol, is the main drug used for hormone therapy for hormone-dependent breast cancer. This ambivalent drug has both antagonist and agonist effects. While tamoxifen blocks tumour growth it can also have an undesirable agonist effect on the genital tract. The uterus is a target organ for this paradoxical action due to proestrogenic stimulation of the endometrium and the myometrium. We observed eleven cases of uterine fibromyoma during treatment with tamoxifen which required hysterectomy due to increased tumour volume. The pathology report on the surgical specimens did not show any evidence of malignancy. Differential diagnosis is based on sarcomatous degeneration of the fibromyoma and presence of intra-myomatous metastases from the breast. Hysterectomy is indicated in menopaused patients with a symptomatic fibromyomatous uterus before starting long-term anti-oestrogen therapy for hormone-dependent breast cancer.