An adenomyoma is an abnormal growth within the muscle tissue lining of the uterus. It is formed when endometrial tissue, the cells that normally make up the innermost lining of the uterus, start growing spontaneously deep within the uterine walls. An adenomyoma is usually benign and does not cause symptoms, though an especially large growth may cause discomfort, tenderness, and heavy bleeding during menstrual periods. Treatment usually involves taking pain medications and using contraceptives to reduce menstrual problems. A very painful mass may need to be removed surgically, either by cutting the growth out or removing the entire uterus via hysterectomy.

The exact causes of adenomyoma growth are unclear. The actual disorder that spurs the development of the mass is called adenomyosis, which is very similar to another type of uterine cell displacement called endometriosis. Adenomyosis does not always result in an adenomyoma. As endometrial cells start invading muscle tissue, they may spread uniformly and cause the tissue lining to thicken. Adenomyomas occur when clusters of cells protrude through the muscle layer.

An adenomyoma may or may not cause symptoms. When symptoms are present, they may include heavy menstrual bleeding and spotting between periods. Adenomyomas can be tender and cause significant pain during menstruation and intercourse. Symptoms tend to worsen over time if they are not assessed and treated in the early stages of adenomyosis.

In many cases, minor problems go undetected until a woman has a routine gynecological exam. The doctor might discover a small lump and arrange for tests to determine if it is an adenomyoma, a fibroid, or a cancerous tumor. Ultrasounds are useful in studying the composition of the mass, and doctors can usually rule out cancer based on imaging tests alone. A biopsy may be necessary if ultrasound tests are inconclusive.

Treatment depends on the size and severity of an adenomyoma. If the growth does not cause problems, a doctor might suggest simply coming in for routine examinations. Minor pain and bleeding can usually be controlled with anti-inflammatory drugs and oral contraceptives. Patients are discouraged from trying to get pregnant because of possible complications.

A small to medium-sized adenomyoma that is clearly defined and causes major symptoms may be removed surgically. In many cases, however, adenomyosis affects a larger area of the uterus than just the noticeable mass. Hysterectomy is the only reliable, certain cure for the condition. Modern surgical techniques allow women to undergo hysterectomies as simple outpatient procedures with short recovery times and very few risks.