Your pathology report for cellular leiomyoma of the uterus

by Jason Wasserman MD PhD FRCPC
September 5, 2025

A cellular leiomyoma is a noncancerous tumour that develops in the muscular wall of the uterus, called the myometrium. Leiomyomas are composed of smooth muscle cells, which are the same type of cells that normally comprise the myometrium. The tumour is called cellular because it contains more muscle cells than the surrounding normal tissue. Cellular leiomyomas are a type of fibroid, which is the common name for all leiomyomas of the uterus.

What are the symptoms of a cellular leiomyoma?

Small cellular leiomyomas usually do not cause any symptoms and may be found incidentally when the uterus is examined for another reason.

Larger cellular leiomyomas can cause:

• Abdominal or pelvic pain.

• A feeling of pressure or fullness in the pelvis.

• Abnormal uterine bleeding, including heavy or prolonged periods.

• Difficulty with urination or bowel movements if the tumour presses on nearby organs.

The severity of symptoms depends on the size and location of the tumour within the uterus.

What is the difference between a cellular leiomyoma and a fibroid?

In the uterus, there is no difference. A fibroid is the common term used to describe a leiomyoma. A cellular leiomyoma is simply a subtype of fibroid that contains more smooth muscle cells than usual.

How is the diagnosis made?

The diagnosis is usually made after tissue from the uterus is removed and examined under the microscope by a pathologist. This may occur after a hysterectomy (removal of the uterus), myomectomy (removal of one or more fibroids), or biopsy.

Sometimes, fibroids are suspected based on symptoms and imaging tests such as ultrasound or MRI. However, the definitive diagnosis of a cellular leiomyoma can only be made by looking at the tumour under the microscope.

What does a cellular leiomyoma look like under the microscope?

When examined under the microscope, a cellular leiomyoma is made up of long, thin spindle cells that resemble normal smooth muscle cells but are more numerous. Pathologists often describe these cells as growing in fascicles, which are long interlacing bundles or chains of cells.

Other common microscopic features include:

• Thick-walled blood vessels.

• Open spaces called cysts.

• Rare mitotic figures, which are tumour cells dividing to make new cells.

Importantly, while cellular leiomyomas contain more cells than usual, they do not show the aggressive features seen in malignant tumours such as leiomyosarcoma.

What does degenerative change mean?

As fibroids grow and age, parts of the tumour may begin to break down. Pathologists call this degenerative change. It is very common in cellular leiomyomas, especially in larger tumours that have been present for a long time. Degenerative changes do not mean the tumour is cancerous.

What does infarct-like necrosis mean?

Some cellular leiomyomas become so large that not all areas of the tumour receive enough blood. Without enough blood supply, some cells die in a process called necrosis. When this pattern of cell death resembles an infarct (an area of tissue death caused by loss of blood supply), it is called infarct-like necrosis.

Infarct-like necrosis is common in fibroids that have been treated with hormone therapy or procedures such as uterine artery embolization, which deliberately blocks blood flow to shrink the tumour. Unlike the type of necrosis seen in malignant tumours, infarct-like necrosis in a cellular leiomyoma does not indicate cancer.

Is a cellular leiomyoma cancer?

No. A cellular leiomyoma is a benign tumour. Even though it contains more cells than usual, it does not behave like cancer and does not spread to other parts of the body. Treatment is usually only required if the tumour causes symptoms.

Questions to ask your doctor

• Was my tumour completely removed?

• Do I need any further treatment for this fibroid?

• Could my fibroid come back or grow in the future?

• What treatment options are available if I develop new symptoms?