Angiosarcoma: Understanding Your Pathology Report

by Bibianna Purgina, MD FRCPC
April 11, 2026

Angiosarcoma is a rare and aggressive type of sarcoma — a cancer that arises from the specialized cells that line the inside of blood and lymphatic vessels. These cells are called endothelial cells. Angiosarcoma can develop in almost any part of the body, but it most commonly arises in the skin of the scalp and face, the breast, the liver, and the soft tissue under the skin. It can also occur in the heart, spleen, and deep soft tissues. Angiosarcoma accounts for roughly 1–2% of all soft tissue sarcomas and affects adults more often than children, with a peak incidence in people over the age of 60. A related but less aggressive vascular tumor is epithelioid hemangioendothelioma.

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 angiosarcoma?

In most cases, angiosarcoma develops without a clear identifiable cause. However, several risk factors are known to increase the likelihood of developing this cancer:

• Chronic lymphedema — Long-term swelling of the tissues caused by damage to or surgical removal of lymph nodes can increase the risk of angiosarcoma in the affected limb. This is sometimes called Stewart-Treves syndrome when it develops in the arm following mastectomy and axillary lymph node removal.
• Prior radiation therapy — Angiosarcoma can arise in tissue that was previously treated with radiation therapy, sometimes many years after the original treatment. Radiation-associated angiosarcoma of the breast is one of the more commonly recognized forms.
• Chronic sun exposure — Prolonged exposure to ultraviolet (UV) radiation from the sun is a risk factor for angiosarcoma arising in the skin of the scalp, face, and neck.
• Chemical exposure — Exposure to vinyl chloride, arsenic, or thorotrast (a formerly used contrast agent) has been linked to angiosarcoma of the liver.

What are the symptoms?

The symptoms of angiosarcoma depend on where in the body the tumor arises. Skin tumors on the scalp or face often appear as a bruise-like discoloration, a raised purple or red patch, or a rapidly enlarging lump. These skin lesions may bleed easily or feel tender to the touch. Breast angiosarcoma typically presents as a painless or mildly tender lump, sometimes with skin discoloration overlying it. Tumors arising in internal organs such as the liver or heart may not cause symptoms until they are large, at which point patients can experience pain, swelling, shortness of breath, or abnormal bleeding. Large tumors anywhere in the body can cause blood-clotting problems, including a tendency to bleed more than expected.

How is the diagnosis made?

The diagnosis of angiosarcoma is made by examining a tissue sample under the microscope. The tissue sample is obtained through a biopsy, a procedure in which a small piece of the tumor is removed using a needle or a small incision. For skin lesions, a punch biopsy or incisional biopsy is typically performed. For tumors in deeper locations, an image-guided needle biopsy using ultrasound or CT is commonly used. The tissue is then sent to a pathologist, who examines it under the microscope.

Under the microscope, angiosarcoma is composed of abnormal blood-vessel-like channels lined by tumor cells that look very different from normal endothelial cells. The tumor cells are larger, darker, and more irregular than normal. Pathologists describe them as showing nuclear atypia. Actively dividing tumor cells, called mitotic figures, are typically present. In some angiosarcomas, particularly high-grade tumors, the cells may grow in solid sheets rather than forming recognizable vessel channels, which can make the diagnosis more challenging. To confirm that the tumor cells are of endothelial origin, pathologists use immunohistochemistry (IHC). This test detects specific proteins inside the cells using special chemical stains. Angiosarcoma cells are typically positive for endothelial markers, including CD31, CD34, and ERG. Once the diagnosis is confirmed by biopsy, imaging — typically CT, MRI, and/or PET-CT — is used to assess the full extent of the tumor and determine whether it has spread to other parts of the body.

Histologic grade

Pathologists do not assign an FNCLCC grade to angiosarcoma. This tumor is already understood to be a high-grade cancer by definition, and the FNCLCC scoring system is not applied because angiosarcoma behaves aggressively regardless of its microscopic appearance. All angiosarcomas have a significant risk of spreading to distant sites. Your pathology report will therefore not include a numeric grade, and this is expected and appropriate for this diagnosis.

Tumor size

The tumor is measured in three dimensions, but only the largest single measurement is typically recorded in your pathology report as the tumor size. For example, a tumor measuring 6.0 cm × 4.5 cm × 3.0 cm would be reported as 6.0 cm. Tumor size is one of the factors used to determine the pathologic tumor stage (pT). Tumors 5 cm or smaller are generally associated with a better prognosis than larger tumors. The final tumor size is measured from the surgically removed specimen, not from a biopsy sample, which represents only a small portion of the tumor.

Tumor extension

Angiosarcoma typically starts within the skin, soft tissue, or an organ, but can grow into adjacent structures as it enlarges. This spread beyond the original site is called tumor extension. The pathologist carefully examines all tissue submitted with the resection specimen to determine whether tumor cells have grown into surrounding muscles, bones, nerves, blood vessels, or organs. Extension into surrounding structures increases the pathologic tumor stage (pT) and may require additional surgery, radiation therapy, or both to achieve local control.

Treatment effect

Some patients with angiosarcoma receive chemotherapy and/or radiation therapy before surgery. This approach is called neoadjuvant therapy, and its purpose is to shrink the tumor before it is removed. After surgery, the pathologist examines the removed tissue and estimates the proportion of the tumor that is non-viable (dead) versus viable (still alive). A tumor that is 90% or more non-viable indicates an excellent response to pre-operative therapy and is associated with a better outcome. When a significant proportion of viable tumor remains, additional treatment after surgery may be considered. Your report will describe the estimated percentage of viable and non-viable tumor.

Lymphovascular invasion

Because angiosarcoma arises from the cells that line blood and lymphatic vessels, the tumor cells are by definition present within vascular spaces. Lymphovascular invasion is therefore an intrinsic feature of this tumor rather than a finding that is separately assessed and reported as it is for most other cancers. Your pathology report is unlikely to include a separate comment about lymphovascular invasion for this reason.

Surgical margins

In pathology, a margin is the edge of tissue removed during surgery. The margin status indicates whether the entire tumor was removed or whether some cancer was left behind. Achieving clear (negative) surgical margins is one of the most important goals of angiosarcoma surgery and a strong predictor of local control.

• Negative margin — No tumor cells are present at the cut edge of the removed tissue. This suggests the tumor was completely removed. The distance between the nearest tumor cells and the margin may also be recorded, as a wider clear margin is associated with a lower risk of local recurrence.
• Close margin — Tumor cells are present very close to the cut edge, but do not reach it. This may increase the risk of local recurrence and may prompt discussion of additional treatment such as radiation therapy.
• Positive margin — Tumor cells are present at the cut edge of the tissue. This means that some cancer may remain in the body. Further surgery or radiation therapy is commonly recommended in this situation.

Angiosarcoma, particularly the scalp and skin form, often grows with poorly defined borders and may extend along tissue planes beyond what is visible to the surgeon. This makes achieving clear margins challenging and is one reason why local recurrence is common.

Lymph nodes

Lymph node spread in angiosarcoma is uncommon but does occur, particularly in skin and scalp angiosarcoma. Lymph nodes are small immune organs that are connected to tissues by tiny vessels. Cancer cells can travel through these vessels and become lodged in nearby lymph nodes. The movement of cancer cells from the tumor to a lymph node or another distant site is called metastasis.

Lymph nodes are removed for examination when they are enlarged or suspicious on imaging. If lymph nodes were removed during your surgery, the pathologist will examine them under the microscope and report on the number of nodes examined, the number containing tumor cells, and the size of the tumor deposit. If tumor cells have broken through the outer capsule of a lymph node into the surrounding tissue, this is called extranodal extension and is associated with a higher risk of further spread.

Biomarker and molecular testing

For most patients with angiosarcoma, there are currently no established biomarker tests that directly guide selection of a targeted drug, as biomarkers do in some other cancers. However, molecular testing is increasingly used in specific settings:

KDR (VEGFR2) and other kinase mutations

A proportion of angiosarcomas — particularly those arising in areas of prior radiation or in association with chronic lymphedema — harbor mutations in the KDR gene, which encodes a protein called vascular endothelial growth factor receptor 2 (VEGFR2). This receptor normally controls blood vessel growth. Mutations that abnormally activate VEGFR2 can promote tumor growth. Anti-angiogenic drugs that target VEGFR — including pazopanib and sorafenib — have shown activity in angiosarcoma and are used in clinical practice, though formal biomarker-driven approval for angiosarcoma is not yet established. Testing for KDR mutations is not yet standard practice but may be performed at specialized centers.

Next-generation sequencing (NGS)

In patients with advanced, recurrent, or metastatic angiosarcoma, comprehensive molecular profiling using next-generation sequencing (NGS) may be performed to identify genetic changes that could make a patient eligible for a clinical trial or targeted therapy. Angiosarcomas secondary to radiation therapy or arising in the breast have shown enrichment for specific mutations that are under active investigation. Your oncologist will discuss whether molecular profiling is appropriate in your situation.

For more information about biomarkers and molecular testing in cancer, visit the Biomarkers and Molecular Testing section of this website.

Pathologic stage (pTNM)

The pathologic stage for angiosarcoma is based on the TNM staging system developed by the American Joint Committee on Cancer (AJCC), 8th edition. This system uses information about the primary tumor (T), lymph nodes (N), and distant metastatic disease (M) to describe the extent of cancer. The M stage — whether the cancer has spread to distant organs such as the lungs — is determined by imaging, not by the pathology report. In general, a higher stage means a more advanced tumor and a less favorable prognosis.

Because angiosarcoma can arise in many different parts of the body, the tumor (pT) staging criteria vary depending on where the tumor starts.

Tumor stage (pT)

Head and neck:

• pT1 — Tumor is 2 cm or smaller.
• pT2 — Tumor is more than 2 cm but 4 cm or smaller.
• pT3 — Tumor is more than 4 cm.
• pT4 — Tumor has grown into surrounding structures such as the bones of the face or skull, the eye, major blood vessels of the neck, or the brain.

Trunk and extremities (chest wall, back, abdomen, arms, and legs):

• pT1 — Tumor is 5 cm or smaller.
• pT2 — Tumor is more than 5 cm but 10 cm or smaller.
• pT3 — Tumor is more than 10 cm but 15 cm or smaller.
• pT4 — Tumor is more than 15 cm.

Thoracic visceral organs (organs inside the chest):

• pT1 — Tumor is confined to one organ.
• pT2 — Tumor has grown into the connective tissue immediately surrounding the organ where it started.
• pT3 — Tumor has grown into at least one adjacent organ.
• pT4 — Multiple separate tumors are present.

Retroperitoneum (the space at the back of the abdominal cavity):

• pT1 — Tumor is 5 cm or smaller.
• pT2 — Tumor is more than 5 cm but 10 cm or smaller.
• pT3 — Tumor is more than 10 cm but 15 cm or smaller.
• pT4 — Tumor is more than 15 cm.

Orbit (the bony socket surrounding the eye):

• pT1 — Tumor is 2 cm or smaller.
• pT2 — Tumor is more than 2 cm but has not grown into the bones surrounding the eye.
• pT3 — Tumor has grown into the bones surrounding the eye or other bones of the skull.
• pT4 — Tumor has grown into the eye itself or surrounding structures, including the eyelids, sinuses, or brain.

• pT0 — No viable tumor found in the resection specimen. This may occur after a complete response to neoadjuvant therapy.
• pTX — The tumor cannot be reliably assessed, for example, because the specimen was received as multiple small fragments.

Nodal stage (pN)

• pN0 — No cancer found in any lymph nodes examined.
• pN1 — Cancer found in one or more regional lymph nodes.
• pNX — Lymph nodes were not assessed.

What is the prognosis?

Angiosarcoma is one of the most aggressive sarcoma subtypes, and outcomes vary significantly depending on the location of the tumor, its stage at diagnosis, and whether complete surgical removal is possible. Overall five-year survival rates across all stages and sites range from approximately 30–40%, though outcomes differ substantially by subgroup.

Localized disease that can be completely removed with clear surgical margins has a better prognosis than advanced or metastatic disease. However, even with apparently localized angiosarcoma, local recurrence is common — particularly for scalp and skin tumors, which often have poorly defined borders and a tendency to spread along tissue planes. Angiosarcoma of the scalp and face tends to have a less favorable prognosis than angiosarcoma arising in other locations. Breast angiosarcoma — both the rare primary form and the more common radiation-associated form — typically has a five-year survival of approximately 30–40%, with radiation-associated cases often behaving more aggressively.

The following features are associated with a worse outcome:

• Positive surgical margins — Tumor cells at the cut edge of the removed tissue significantly increase the risk of local recurrence and are one of the strongest adverse prognostic factors.
• Larger tumor size — Tumors greater than 5 cm are associated with a higher risk of spread and death from disease.
• Metastatic disease at diagnosis — The lungs, liver, bone, and lymph nodes are the most common sites of distant spread. Patients with metastatic disease at presentation have a median survival of less than 12 months with current treatments.
• Deep location — Angiosarcomas arising in deep soft tissue or internal organs tend to be diagnosed at a larger size and are more difficult to remove completely compared with skin tumors.
• Radiation-associated angiosarcoma — Tumors arising in previously irradiated tissue, particularly breast angiosarcoma following radiation therapy for breast cancer, often behave more aggressively than primary angiosarcomas.

What happens after the diagnosis?

After the diagnosis is confirmed, care is best managed by a multidisciplinary team that includes a surgical oncologist or orthopedic oncologist, a medical oncologist with experience in sarcoma, and a radiation oncologist. Referral to a sarcoma center or cancer center with specific expertise in rare soft tissue tumors is strongly recommended, as this type of cancer requires specialized management.

Surgery is the main treatment for localized angiosarcoma. The goal is to remove the entire tumor with clear margins. Because angiosarcoma — particularly scalp and skin angiosarcoma — often extends beyond the visible lesion, wide margins are typically required. In some cases, multiple re-excisions may be needed to achieve clear margins.

Radiation therapy is commonly used alongside surgery for angiosarcoma, either before surgery (neoadjuvant) to shrink the tumor or after surgery (adjuvant) to reduce the risk of local recurrence. For scalp and head-neck angiosarcoma, radiation therapy is generally considered part of the standard treatment approach given the high rate of local recurrence with surgery alone.

Chemotherapy is used for locally advanced, unresectable, or metastatic disease. The most commonly used regimens include doxorubicin (either alone or in combination with ifosfamide), and paclitaxel — a taxane chemotherapy agent that has shown particular activity against angiosarcoma of the skin and scalp, with response rates of approximately 60–70% in some studies. Gemcitabine combined with docetaxel is another option used in later lines of therapy.

Anti-angiogenic targeted therapy with agents such as pazopanib, sorafenib, or sunitinib has shown activity in angiosarcoma in clinical studies and is used in clinical practice, particularly for patients who are not candidates for or have progressed on chemotherapy. These drugs work by blocking the signals that promote blood vessel growth, which is central to angiosarcoma biology.

Clinical trial enrollment is actively encouraged for patients with advanced, recurrent, or metastatic angiosarcoma, and for any patient whose tumor has not responded to standard treatment. Research into new targeted therapies, immunotherapy, and combinations is ongoing. Your oncologist can discuss whether a clinical trial is available and appropriate for your situation.

Surveillance after treatment includes regular physical examination, cross-sectional imaging (CT or MRI), and monitoring of the primary tumor site. The lungs are the most common site of distant spread and are monitored with CT of the chest. The schedule and duration of surveillance will be tailored to your specific situation by your treatment team.

Questions to ask your doctor

• Where exactly did the angiosarcoma arise, and has it spread to any lymph nodes or other organs?
• What is the pathologic stage of my tumor?
• Were the surgical margins clear, and how close was the tumor to the edge of the removed tissue?
• Is this a primary angiosarcoma or one related to prior radiation therapy or lymphedema?
• Will I need additional surgery, radiation therapy, or chemotherapy based on these results?
• Was the tumor tested with immunohistochemistry to confirm the diagnosis, and were there any unusual or unexpected findings?
• Should molecular profiling (next-generation sequencing) be performed on my tumor to look for treatment-relevant mutations?
• What is the risk of local recurrence, and how will that be monitored?
• Are there clinical trials I should consider for this type of sarcoma?
• Should I be seen at a sarcoma specialty center, and would a second opinion on my pathology be helpful?
• What imaging will be used to monitor for spread to the lungs or other organs, and how often will I be scanned?
• Are there any factors in my pathology report — such as tumor size, margin status, or molecular findings — that particularly affect my prognosis?