**Core Concept**
Tamoxifen is a selective estrogen receptor modulator (SERM) used in the treatment and prevention of breast cancer. It acts by binding to estrogen receptors on breast cancer cells, thereby inhibiting estrogen's proliferative effects.

**Why the Correct Answer is Right**
Tamoxifen is known to cause endometrial cancer, deep vein thrombosis, and pulmonary embolism as side effects. This is due to its partial estrogen agonist activity in certain tissues, such as the uterus, where it can stimulate cell growth. However, tamoxifen's anti-estrogenic effects in breast tissue make it an effective treatment for breast cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** Hot flashes - This is incorrect because hot flashes are a common side effect of tamoxifen, likely due to its anti-estrogenic effects on the brain.

**Option B:** Endometrial cancer - This is incorrect because endometrial cancer is actually a known side effect of tamoxifen, resulting from its partial estrogen agonist activity in the uterus.

**Option C:** Pulmonary embolism - This is incorrect because pulmonary embolism is a known side effect of tamoxifen, likely due to its increased risk of venous thromboembolism.

**Clinical Pearl / High-Yield Fact**
Tamoxifen's side effect profile highlights the complex interplay between estrogen receptors and different tissues in the body.

**Correct Answer:** D. Hot flashes