Glomangiopericytoma: Understanding Your Pathology Report

Section Editor: Jason Wasserman MD PhD FRCPC
July 14, 2026

Glomangiopericytoma is a rare tumor that develops in the soft tissues of the nasal cavity or paranasal sinuses, the hollow spaces around the nose. It usually behaves in a noncancerous way, growing slowly and staying confined to the area where it started. In rare cases, however, it can behave in a more concerning way, growing into nearby tissues or, very uncommonly, spreading to other parts of the body. For this reason, pathologists classify glomangiopericytoma as a borderline tumor, meaning it has features that fall between benign (noncancerous) and malignant (cancerous) tumors. It most often occurs on one side of the nasal cavity, especially along the nasal septum or the turbinates, and it may extend into nearby sinuses such as the ethmoid or maxillary sinuses. This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes glomangiopericytoma?

The exact cause of glomangiopericytoma is not known, but most tumors have a mutation (change) in a gene called CTNNB1. This gene controls the production of a protein called beta-catenin, which helps regulate how cells grow and divide. In glomangiopericytoma, the mutation causes beta-catenin to accumulate in the cell nucleus, which increases the activity of another protein, cyclin D1, that promotes cell growth. These molecular changes are a key feature of the tumor and help explain why it develops, although they do not make it behave in a cancerous way.

What are the symptoms?

Most people with glomangiopericytoma notice symptoms related to blockage or bleeding inside the nose. Common symptoms include nasal obstruction (difficulty breathing through one side of the nose), nosebleeds, and a feeling of pressure or fullness in the face or sinuses. Less commonly, some people have sinus infections or nasal discharge. Very rarely, glomangiopericytoma has been associated with a condition called oncogenic osteomalacia, a form of bone weakening caused by certain substances released by the tumor.

How is the diagnosis made?

The diagnosis of glomangiopericytoma is made by a pathologist after examining a tissue sample from the tumor under the microscope. The sample may be taken by biopsy during nasal endoscopy or after the tumor has been surgically removed.

Under the microscope, glomangiopericytoma is usually well-defined and located just beneath the surface lining of the nasal cavity. It is made up of oval or spindle-shaped cells that grow in a patternless way around many thin-walled blood vessels. These vessels often branch in a “staghorn” shape, giving the tumor a rich vascular appearance. The supporting tissue, called the stroma, often shows hyalinization, a glassy pink change around the blood vessels. The tumor cells usually look uniform, with only mild variation in size and shape. Mitotic figures (dividing cells) are seen occasionally but not in high numbers, and necrosis (dead tumor tissue) is uncommon. The tumor may also contain scattered inflammatory cells, such as eosinophils and mast cells, along with red blood cells that have leaked from nearby vessels. Pathologists describe glomangiopericytoma as showing perivascular myoid differentiation, meaning the tumor cells grow around small blood vessels and resemble smooth muscle cells.

To confirm the diagnosis, the pathologist uses immunohistochemistry, a test that uses specially labeled antibodies to detect proteins in the tumor cells. The tumor cells in glomangiopericytoma typically stain strongly for smooth muscle actin (SMA) and muscle-specific actin (MSA), confirming their muscle-like (myoid) nature, and show nuclear beta-catenin, LEF1, and cyclin D1, reflecting the CTNNB1 gene mutation. The tumor cells do not stain for markers found in other tumor types, such as STAT6, S100, SOX10, cytokeratins, desmin, or CD31. These findings help distinguish glomangiopericytoma from other spindle cell tumors that can occur in the nasal cavity, including solitary fibrous tumor, schwannoma, and biphenotypic sinonasal sarcoma.

On imaging studies such as CT or MRI, glomangiopericytoma often appears as a polyp-like growth within the nasal cavity or sinuses, and it may cause remodeling or erosion of nearby bone due to slow, steady pressure. Surgeons usually describe the tumor as a soft, fleshy, red-pink mass that can bleed easily during removal.

Surgical margins

When glomangiopericytoma is surgically removed, the margin is the edge of normal tissue at the outer surface of the specimen. After surgery, the pathologist examines the margins under the microscope to see whether any tumor cells are present at the cut surface.

Negative margin — No tumor cells are seen at the cut edge. This suggests the tumor was completely removed.
Positive margin — Tumor cells are present at the cut edge. This is associated with a higher risk that the tumor will come back (recur) in the same area.

In the nasal cavity and paranasal sinuses, it is often difficult to remove the tumor in one piece because of the complex anatomy, and the specimen is frequently taken out in several smaller fragments. When this happens, the pathologist may not be able to reliably assess the margins, because the exact orientation of each piece cannot be determined. For this reason, close follow-up with imaging and nasal endoscopy after surgery is important, even when the margins cannot be fully evaluated.

What is the prognosis?

Prognosis refers to the likely long-term outcome after a diagnosis. Glomangiopericytoma is an indolent (slow-growing) tumor with an overall excellent outlook, and most people are cured after complete surgical removal. However, about 20 percent of cases can come back (recur) in the same area, sometimes many years after the first surgery. Recurrence is most likely when the tumor was not completely removed or when it shows features that suggest a higher risk. These features include:

Large size — Tumors larger than 5 cm.
Bone involvement — Invasion of bone or extension into nearby areas such as the base of the skull.
Active growth — Areas of necrosis or a high rate of cell division (more than 4 mitotic figures per 2 mm²).
Abnormal-looking cells — Marked variation in the size and shape of the cells (pleomorphism).

Because recurrences can appear even a decade or more after surgery, long-term follow-up with regular examinations is recommended.

What happens after the diagnosis?

Surgery to remove the tumor is the main treatment for glomangiopericytoma, and the goal is to remove the entire tumor with a small rim of normal tissue to lower the chance of it coming back. Because these tumors almost never spread to other parts of the body, radiation therapy and chemotherapy are rarely needed, though radiation may be considered for tumors that cannot be completely removed with surgery. After treatment, long-term follow-up with imaging and nasal endoscopy is important, because glomangiopericytoma can recur many years later. Care is usually provided by an ear, nose, and throat (ENT) surgeon, with other specialists involved as needed.

Questions to ask your doctor

Where in my nasal cavity or sinuses was the tumor located?
Was the tumor completely removed, and were the surgical margins clear?
Did my tumor show the typical beta-catenin changes?
Did my tumor have any of the features that increase the risk of it coming back, such as large size, bone involvement, or a high rate of cell division?
What is my risk that this tumor could come back?
How often should I have follow-up exams or imaging, and for how long?
What symptoms should prompt me to contact my doctor between visits?
Would radiation therapy ever be needed in my case, and if so, why?
Which specialists will be involved in my care?
Is there any risk that this tumor could spread to other parts of the body?