Intravenous leiomyomatosis (IVL) is a benign smooth muscle tumor of the uterus that grows within the veins but does not invade the surrounding tissue. IVL usually starts in the veins of the uterus and can extend into the inferior vena cava and ultimately into the right side of the heart, resulting in death The abnormal smooth muscle cells that cause IVL express estrogen and progesterone receptors and tumor growth thus appears to respond to these hormones. Although this is a benign condition, many affected individuals require surgery to remove the excess tissue in the uterus and heart. The exact cause of IVL remains unknown. IVL is rare, with only about 200 cases reported in the medical literature.

IVL most often does not cause detectable signs or symptoms. In fact, they may be found by chance during surgery. When symptoms do arise, they can include abnormal uterine bleeding, lower abdominal tenderness, and venous thrombosis. When IVL in the uterus is exposed to venous blood that flows to the heart, it usually grows slowly and may reach the heart undetected. When IVL reaches the heart, it can result in pulmonary embolisms, cardiac failure, fainting, and in some cases, sudden death. Most people do not experience symptoms until the IVL reaches the heart.

The mainstay of treatment for IVL is surgery to remove the tumor and its spread throughout the body. The use of anti-estrogen therapy, such as tamoxifen, has also been suggested. Surgery requires the complete removal of the tumor, since incomplete removal may result in a recurrence and hence further surgery or even death. Many affected individuals undergo a hysterectomy; bilateral oophorectomy is also suggested because these tumors are estrogen dependent. Part of a tumor left inside the pelvic veins at the time of hysterectomy can extend towards the right side of the heart, leading to obstruction and other adverse events later in life. The median time between hysterectomy to the diagnosis of IVL with cardiac involvement is 4 years. Once there is cardiac involvement, a patient may require open-heart surgery to remove the IVL from the affected areas.