Angioleiomyoma: Understanding Your Pathology Report

Section Editor: Bibianna Purgina MD FRCPC
September 25, 2026

An angioleiomyoma is a noncancerous tumor made of smooth muscle cells, the same type of muscle found in the walls of blood vessels. Under the microscope, the tumor cells form bundles wrapped around many small blood vessels, a feature that defines this diagnosis.

Angioleiomyomas usually develop in the deep layer of the skin or in the fat just beneath it. They do not spread to other parts of the body, and removing the lump is normally curative. Your report may use one of the alternative names for this tumor, angiomyoma or vascular leiomyoma.

This tumor is one of the few lumps under the skin that are often painful, which is why many are removed.

This article explains how an angioleiomyoma is diagnosed and what the subtype, size, and margins in your pathology report mean.

Where does an angioleiomyoma develop?

Angioleiomyomas are most common in the arms and legs, particularly the lower leg and ankle. They also occur in the head and neck, including inside the nose or mouth, and on the chest or back.

These tumors are usually diagnosed in adults between 30 and 60 years old. Tumors of the leg are more common in women, and tumors of the head and neck are more common in men.

What are the symptoms of an angioleiomyoma?

An angioleiomyoma usually appears as a small, firm, well-defined lump beneath the skin that grows slowly over months or years. Most are less than 3 cm across.

About half of people have pain or tenderness. The pain may be triggered by touch, pressure, or cold weather, and it can be out of proportion to the lump’s size. Many angioleiomyomas are only noticed once they become painful.

What causes an angioleiomyoma?

The cause is not known. Most angioleiomyomas develop by chance, without any identifiable risk factor, and they are not inherited.

Some studies suggest that minor injury or slowed blood flow in the veins may play a part, but the evidence is limited. A few tumors show changes involving chromosomes 6, 13, and 21, and a small number have a rearrangement of a gene called NOTCH2, which is also seen in glomus tumors. These changes are not used to make the diagnosis.

How is the diagnosis made?

The diagnosis of an angioleiomyoma is made after a pathologist examines tumor tissue under the microscope. Because these tumors are small and sit close to the skin, most are removed whole in a minor procedure, and the diagnosis is made afterward. Imaging such as ultrasound or MRI may be done first if the lump is deep, unusually painful, or close to an important structure.

Under the microscope, an angioleiomyoma is made of smooth muscle cells that closely resemble normal muscle and are arranged around many blood vessels. The cells look bland and uniform. There is no dead tumor tissue, and dividing cells are absent or very rare.

Some tumors also contain small amounts of fat, calcification, or scattered enlarged nuclei. These are expected changes and do not affect the outlook.

What are the subtypes of angioleiomyoma?

Your report may name a subtype, which describes the pattern of blood vessels within the tumor. All three behave the same way and are noncancerous:

Solid. Tightly packed muscle bundles with small, slit-like vessels. This subtype is most common in the leg.
Venous. Vessels with thicker muscular walls that blend into the surrounding muscle. This subtype is more common in the head and neck.
Cavernous. Large, widened vascular spaces separated by smooth muscle. This subtype more often occurs in the arm.

Some tumors contain a mixture of these patterns. The subtype does not change treatment or the outlook.

Immunohistochemistry

Immunohistochemistry is a test that uses antibodies to show which proteins cells make. For an angioleiomyoma, it confirms that the tumor is made of smooth muscle. Your report may include some of the following:

SMA, calponin, and h-caldesmon. These smooth muscle proteins are strongly positive.
Desmin. This protein may be positive, although staining is sometimes weak or patchy.
HMB-45 and Melan-A. These markers of pigment-producing cells are negative, even in tumors that contain some fat. A positive result would suggest a different tumor.

Tumor size

Angioleiomyomas are usually less than 3 cm across. Size does not change how this tumor behaves, since it is noncancerous regardless of its size. A larger tumor may be more noticeable or uncomfortable.

Margins

A margin is the edge of tissue cut by the surgeon. Margins can be assessed only after the surgeon removes the entire tumor.

A negative margin means no tumor cells were seen at the cut edge. A positive margin means tumor cells reach it. For an angioleiomyoma, a positive margin does not carry the meaning it does for cancer, and the tumor rarely comes back even when a margin is positive.

What is the prognosis?

The outlook is excellent. An angioleiomyoma is noncancerous, does not spread, and does not turn into cancer. Complete removal is curative, and recurrence is uncommon.

When the tumor is painful, the pain usually settles after removal.

What happens after the diagnosis?

Most people need no treatment beyond removal of the lump. Long-term follow-up is not usually required.

Your doctor may suggest a follow-up visit if the tumor was in a sensitive area, if the margins were close or positive, or if symptoms return. New lumps elsewhere are new tumors, not a return of the one removed.

Questions to ask your doctor

Was the tumor completely removed, and were the margins negative?
Which subtype does my report describe, and does it matter?
Is my pain likely to settle now that the lump is out?
Is there a chance this tumor could come back?
Do I need any follow-up or imaging?
If a new lump appears, should I have it checked?