The nurse is administering an estrogen blocker to a client diagnosed with advanced breast cancer. Which of the following side effects will the nurse caution the client regarding?

A. Tendon Rupture: Tendon rupture is not a commonly associated side effect of estrogen blockers. While some medications, particularly corticosteroids or fluoroquinolones, may carry a risk of tendon issues, estrogen blockers like tamoxifen or aromatase inhibitors primarily influence hormone-driven cancer cell growth and do not have a direct link to tendon rupture. Therefore, cautioning the client regarding tendon rupture is not a priority when administering estrogen blockers. B. Increase risk of lymphomas: Estrogen blockers are primarily associated with changes in estrogen receptor activity, which can affect various bodily systems. However, the increased risk of lymphoma is not a major concern associated with these drugs. Side effects related to estrogen blockers usually involve blood clots, hot flashes, and menstrual irregularities, not an increased incidence of lymphomas. This makes cautioning clients about lymphoma less relevant. C. Thromboembolic events: Thromboembolic events, such as deep vein thrombosis (DVT), pulmonary embolism (PE), and stroke, are a well-known and serious side effect of estrogen blockers like tamoxifen. These drugs can increase the risk of clotting due to their effects on the coagulation system. Estrogen has pro-thrombotic effects, and estrogen blockers can exacerbate this, making it essential to caution clients about signs and symptoms of clots and to monitor for such events during therapy. D. Photosensitivity: Photosensitivity is not a significant concern with estrogen blockers. Although some medications can cause increased sensitivity to sunlight, this is not a major side effect for most estrogen blockers. The more pressing concerns typically involve thromboembolic risks, as well as potential effects on mood, bone density, and menstrual function. Thus, while sun protection is important in general, photosensitivity is not a primary issue with estrogen blockers in the treatment of breast cancer.