Leiomyoma of the uterus

by Jason Wasserman MD PhD FRCPC
September 13, 2023

What is a leiomyoma of the uterus?

A leiomyoma is a non-cancerous tumour that starts in the wall of the uterus. The tumour is made up of specialized smooth muscle cells that are normally found in a part of the uterus called the myometrium. Leiomyomas are very common tumours and they usually occur in women between 20 and 50 years old. Another name for leiomyoma of the uterus is fibroid.

What are the symptoms of a leiomyoma in the uterus?

Small leiomyomas typically do not cause any symptoms. Larger tumours can cause symptoms such as abdominal pain, pressure, and vaginal bleeding.

What is the difference between a leiomyoma and a fibroid?

In the uterus, there is no difference between a leiomyoma and a fibroid. Both terms are used to describe the same type of non-cancerous tumour.

How is the diagnosis of leiomyoma in the uterus made?

Leiomyomas are often diagnosed after all or a part of the uterus has been removed and tissue has been examined under the microscope by a pathologist. For many patients, the uterus is removed for other reasons and the leiomyoma is found incidentally.

What does a leiomyoma look like under the microscope?

When examined under the microscope, a leiomyoma is made up of long thin cells called spindle cells. These cells are often described as growing in fascicles which are long interconnecting chains of cells. Thick-walled blood vessels and open spaces called cysts are commonly seen. Rare mitotic figures (tumour cells dividing to create new tumour cells) may be also seen.

What is a subserosal leiomyoma?

Pathologists describe a leiomyoma as subserosal if the tumour is found just under a thin layer of tissue on the outside surface of the uterus called the serosa.

What is an intramural leiomyoma?

Pathologists describe a leiomyoma as intramural if the tumour is located within the wall of the uterus in a layer of tissue called the myometrium.

What is a submucosal leiomyoma?

Pathologists describe a leiomyoma as submucosal if the tumour is located just below a thin layer of tissue on the inside surface of the uterus called the endometrium.

What does it mean if a leiomyoma shows degenerative changes?

Degenerative change is a term pathologists use to describe the breakdown of tissue over time. It is very common to see degenerative changes in a leiomyoma, especially larger ones that have been growing for a long time.

What does it mean if a leiomyoma shows infarct-like necrosis?

Some leiomyomas grow so large that blood cannot get to all of the cells in the tumour. The cells that do not receive blood undergo a type of cell death called necrosis and the area of the tumour that dies is described as an infarct. Infarct-like necrosis is very common in leiomyomas that have been treated with hormone therapy or embolization.

What does it mean if a leiomyoma is described as mitotically active?

Mitotically active means that dividing tumour cells called mitotic figures were seen within the tumour. Mitotically active leiomyomas are more common in younger women, pregnant women, and in women previously treated with certain medications such as tamoxifen and progesterone. Despite the increased mitotic activity, these tumours are still non-cancerous.

What does it mean if a leiomyoma contains atypical tumour cells?

The tumour cells in a leiomyoma usually look very similar to the smooth muscle cells normally found in the myometrium of the uterus. However, when examined under the microscope, some leiomyomas contain tumour cells that are larger and darker than normal smooth muscle cells. pathologists describe these cells as atypical. Although they look abnormal, atypical tumour cells are not cancer cells and are not associated with a worse prognosis.