Your pathology report for angioleiomyoma

by Jason Wasserman MD PhD FRCPC
December 9, 2025

Angioleiomyoma is a benign (noncancerous) soft tissue tumour that develops from smooth muscle cells, the same cells found in the walls of blood vessels. These tumours usually arise in the dermis (the deep layer of the skin) or subcutis (the fat just beneath the skin). Under the microscope, the tumour cells grow in bundles surrounding numerous small blood vessels, which is a key feature of this diagnosis.

Angioleiomyoma is closely related to another benign tumour, myopericytoma, and in some cases, the two tumours share overlapping features. Acceptable alternative names include angiomyoma and vascular leiomyoma. Because angioleiomyoma is benign, it does not metastasize, and surgical removal is generally curative.

Where in the body does angioleiomyoma occur?

Angioleiomyomas are most common in the arms and legs, especially the lower extremities. They can also occur in the head and neck, including inside the nose or mouth, as well as on the trunk (chest or back).

Pathologists describe three microscopic subtypes—solid, venous, and cavernous—based on the pattern of blood vessels in the tumour. These patterns often correlate with location: solid tumours usually occur on the legs, venous types are more common in the head and neck, and cavernous types may appear in the upper limbs. All types are benign and behave similarly.

What are the symptoms?

Angioleiomyoma typically appears as a small, firm, well-defined lump beneath the skin. The tumour grows slowly, often over months or years. About half of patients experience pain or tenderness, which may worsen with touch, cold weather, or pressure.

Because the tumour is usually small—often less than 3 cm—it may go unnoticed until it becomes painful or bothersome.

What causes angioleiomyoma?

The exact cause is not known. Most angioleiomyomas arise sporadically, meaning they are not inherited and develop without any identifiable risk factors. Some studies suggest that minor trauma or venous stasis (slowed blood flow) may contribute, but evidence is limited.

A small number of tumours have shown chromosomal changes involving chromosomes 6, 13, and 21, although these findings are not consistent across cases. Rarely, rearrangements in a gene called NOTCH2, commonly seen in glomus tumours, have been reported. However, these molecular changes are not used in routine diagnosis, and their role in tumour development remains unclear.

How is this diagnosis made?

Imaging

Imaging is not always required because the tumour is typically small and located close to the skin. When performed—usually via ultrasound or MRI—the imaging shows a well-circumscribed mass that appears benign. Imaging may be used if the tumour is deep, painful, or located near important structures.

Biopsy

A diagnosis of angioleiomyoma is usually confirmed after a biopsy or after the tumour is removed surgically. A pathologist examines the tissue under a microscope to determine the tumour type. Because these tumours are small and benign, many are removed entirely without prior biopsy.

Microscopic features

Under the microscope, angioleiomyoma consists of well-differentiated smooth muscle cells arranged around numerous blood vessels. The tumour cells look bland and uniform, with no aggressive features. Three microscopic patterns exist:

• Solid type – tightly packed smooth muscle bundles with small, slit-like vessels.

• Venous type – vessels with thicker muscular walls that blend with the surrounding smooth muscle.

• Cavernous type – large, dilated vascular spaces separated by smooth muscle.

Some tumours show a mixture of patterns. Additional benign changes—such as small fat deposits, calcification, or mild degenerative nuclear atypia—may be seen and do not affect prognosis.

Immunohistochemistry

Immunohistochemistry (IHC) uses antibodies to detect specific proteins in tumour cells. Angioleiomyoma typically shows strong positivity for smooth muscle markers, including smooth muscle actin (SMA), calponin, and h-caldesmon, supporting its smooth muscle origin.

Desmin may be positive, but it is sometimes only weak or patchy. Markers associated with melanocytic tumours, such as HMB45 and melan-A, are negative, even in tumours that contain small amounts of fat.

Tumour size

Angioleiomyomas are usually less than 3 cm in size. Tumour size does not affect behaviour because the tumour is benign; however, larger tumours may be more uncomfortable or noticeable.

Margins

A margin is the edge of tissue removed during surgery. Margins are assessed only after the tumour is completely excised.

A negative margin means no tumour cells were seen at the cut edge, suggesting the tumour was entirely removed. A positive margin means the tumour reaches the surgical edge. Even with a positive margin, recurrence is very uncommon, but your doctor may discuss whether further treatment or observation is appropriate.

What happens after the diagnosis?

Most patients require no further treatment beyond surgical removal. Angioleiomyoma rarely recurs after complete excision, and long-term follow-up is minimal unless symptoms return. Pain typically resolves once the tumour is removed.

If the tumour was located in a sensitive area or the margins were close or positive, your doctor may recommend a follow-up visit to ensure healing and monitor for an infrequent recurrence.

Questions to ask your doctor

• Was the tumour completely removed, and were the margins clear?

• Do I need any follow-up or imaging after surgery?

• What symptoms should I watch for that might suggest recurrence?

• Can this tumour come back or cause problems in the future?