Thrombocytopenia and/or leukopenia may occur. Neutropenia and pancytopenia reported rarely. Endometrial hyperplasia, polyps, endometriosis, uterine fibroids, and ovarian cysts occurred. May increase risk of uterine or endometrial cancer. Amenorrhea, menstrual irregularities reported with tamoxifen use. Liver abnormalities such as cholestasis, fatty liver, hepatitis, and hepatic necrosis occurred. Hepatocellular carcinomas reported in some studies (relationship to treatment unclear). Decreased visual acuity, retinal vein thrombosis, retinopathy, corneal changes, color perception changes and increased incidence of cataracts reported. Serious and life-threatening events (including stroke, pulmonary emboli, and uterine malignancy) occurred during use for cancer risk reduction (these events are rare). In patients already diagnosed with breast cancer, benefits of tamoxifen use are greater than risks. Increased incidence of thromboembolic events, including DVT and pulmonary embolism, associated with use for breast cancer. Risk increased with concomitant chemotherapy. Use with caution in history of thromboembolic events. Tamoxifen use may be associated with changes in bone mineral density and effects may be dependent upon menstrual status. In postmenopausal women, tamoxifen use associated with protective effect on bone mineral density. In premenopausal women, decline in bone mineral density observed in women who continued to menstruate (may be associated with increased risk of fractures). Use with caution in hyperlipidemias (infrequent postmarketing cases of hyperlipemias reported). Local disease flare and increased bone and tumor pain may occur. May be associated with (good) tumor response. In bone metastasis, hypercalcemia occurred usually within a few weeks of therapy initiation.