Angiosarcoma

by Bibianna Purgina, MD FRCPC
July 23, 2024

Background:

Angiosarcoma is an aggressive type of cancer that develops from specialized endothelial cells normally found on the inside of blood vessels. The most common locations are the scalp, skin, and soft tissue under the skin. Other body sites that can be affected include the breast, liver, lung, and spleen.

What type of cancer is angiosarcoma?

Angiosarcoma is a type of sarcoma. Sarcomas are cancers that develop from tissues such as bones, muscles, blood vessels, and connective tissue.

What causes angiosarcoma?

Several risk factors can increase a person’s chance of developing angiosarcoma. The first is chronic sun exposure, which is why angiosarcomas often develop in the skin. The second is chronic lymphedema, which is the swelling of tissues that can develop after removing lymph nodes. Finally, some angiosarcomas develop in an area that has previously been treated by radiation therapy.

What are the symptoms of angiosarcoma?

The symptoms of angiosarcoma depend on the location of the tumour. Tumours located in the skin tend to grow quickly and often feel painful to the touch. Larger tumours can cause anaemia (decreased red blood cells in the blood) and other blood abnormalities, including persistent bleeding or blood clots.

How is this diagnosis made?

The first diagnosis of an angiosarcoma is usually made after a small tumour sample is removed in a procedure called a biopsy. The biopsy tissue is then sent to a pathologist, who examines it under a microscope. After the diagnosis is made, most patients are offered surgery to remove the tumour completely.

Microscopic features of this tumour

When examined under the microscope, angiosarcoma is made up of abnormal-appearing blood vessels. The cells lining the inside of blood vessels are called endothelial cells. The endothelial cells in angiosarcoma are larger, darker, and more variable than normal endothelial cells. Pathologists describe these cells as atypical. Dividing tumour cells called mitoses are usually also seen.

Grade

All angiosarcomas are aggressive tumours that commonly spread to other parts of the body regardless of the microscopic features of the tumour. For that reason, angiosarcoma is not given a tumour grade.

Tumour size

The tumour is measured in three dimensions but only the largest dimension is typically included in your report. For example, if the tumour measures 5.0 cm by 3.2 cm by 1.1 cm, the report may describe the tumour size as 5.0 cm in the greatest dimension. Tumour size is important because it determines the pathologic tumour stage (pT). Tumours less than 5 cm are associated with a better prognosis.

Tumour extension

Angiosarcomas can grow into or around organs and bones. Your pathologist will examine samples of the surrounding organs and tissues under the microscope to look for cancer cells. Any surrounding organs or tissue that contains cancer cells will be described in your report. Tumour extension is important because it determines the pathologic tumour stage (pT).

Treatment effect

If you received chemotherapy and/or radiation therapy before the operation to remove your tumour, your pathologist will examine all the tissue sent to pathology to see how much of the tumour is still alive (viable). Most commonly, your pathologist will describe the percentage of dead tumour.

Margins

In pathology, a margin is the edge of tissue removed during tumour surgery. The margin status in a pathology report is important as it indicates whether the entire tumour was removed or if some was left behind. This information helps determine the need for further treatment.

Pathologists typically assess margins following a surgical procedure, like an excision or resection, that removes the entire tumour. Margins aren’t usually evaluated after a biopsy, which removes only part of the tumour. The number of margins reported and their size—how much normal tissue is between the tumour and the cut edge—vary based on the tissue type and tumour location.

Pathologists examine margins to check if tumour cells are present at the tissue’s cut edge. A positive margin, where tumour cells are found, suggests that some cancer may remain in the body. In contrast, a negative margin, with no tumour cells at the edge, suggests the tumour was fully removed. Some reports also measure the distance between the nearest tumour cells and the margin, even if all margins are negative.

Lymph nodes

Lymph nodes are small immune organs found throughout the body. Cancer cells can spread from a tumour to lymph nodes through small lymphatic vessels. For this reason, lymph nodes are commonly removed and examined under a microscope to look for cancer cells. The movement of cancer cells from the tumour to another part of the body, such as a lymph node, is called a metastasis.

Cancer cells typically spread first to lymph nodes close to the tumour, although lymph nodes far away from the tumour can also be involved. For this reason, the first lymph nodes removed are usually close to the tumour. Lymph nodes further away from the tumour are only typically removed if they are enlarged and there is a high clinical suspicion that there may be cancer cells in the lymph node.

If any lymph nodes were removed from your body, they will be examined under the microscope by a pathologist, and the results of this examination will be described in your report. The examination of lymph nodes is important for two reasons. First, this information determines the pathologic nodal stage (pN). Second, finding cancer cells in a lymph node increases the risk that cancer cells will be found in other parts of the body in the future. As a result, your doctor will use this information when deciding if additional treatment, such as chemotherapy, radiation therapy, or immunotherapy, is required.

Some helpful definitions:

• Positive: Positive means that cancer cells were found in the lymph node being examined.
• Negative: Negative means that no cancer cells were found in the lymph node being examined.
• Deposit: The term deposit describes a group of cancer cells inside a lymph node. Some reports include the size of the largest deposit. A similar term is “focus”.
• Extranodal extension: Extranodal extension means that the tumour cells have broken through the capsule on the outside of the lymph node and have spread into the surrounding tissue.

Pathologic stage (pTNM)

​The pathologic stage for angiosarcoma is based on the TNM staging system, an internationally recognized system created by the American Joint Committee on Cancer. This system uses information about the primary tumour (T), lymph nodes (N), and distant metastatic disease (M)  to determine the complete pathologic stage (pTNM). Your pathologist will examine the tissue submitted and give each part a number. In general, a higher number means a more advanced disease and a worse prognosis.

Tumour stage (pT) for angiosarcoma

The tumour stage for angiosarcoma varies based on the body part involved. For example, a 5-centimetre tumour that starts in the head will be given a different tumour stage than a tumour that starts deep in the back of the abdomen (the retroperitoneum). However, in most body sites, the tumour stage includes the tumour size and whether the tumour has grown into surrounding body parts.

Tumour stage for tumours starting in the head and neck:

T1 – The tumour is no greater than 2 centimetres in size.
T2 – The tumour is between 2 and 4 centimetres in size.
T3 – The tumour is greater than 4 centimetres in size.
T4 – The tumour has grown into surrounding tissues such as the bones of the face or skull, the eye, the larger blood vessels in the neck, or the brain.

Tumour stage for tumours starting on the outside of the chest, back, or stomach and the arms or legs (trunk and extremities):

T1 – The tumour is no greater than 5 centimetres in size.
T2 – The tumour is between 5 and 10 centimetres in size.
T3 – The tumour is between 10 and 15 centimetres in size.
T4 – The tumour is greater than 15 centimetres in size.

Tumour stage for tumours starting in the abdomen and organs inside the chest (thoracic visceral organs):

T1 – The tumour is only seen in one organ.
T2 – The tumour has grown into the connective tissue surrounding the organ from which it started.
T3 – The tumour has grown into at least one other organ.
T4 – Multiple tumours are found.

Tumour stage for tumours starting in the space at the very back of the abdominal cavity (retroperitoneum):

T1 – The tumour is no greater than 5 centimetres in size.
T2 – The tumour is between 5 and 10 centimetres in size.
T3 – The tumour is between 10 and 15 centimetres in size.
T4 – The tumour is greater than 15 centimetres in size.

Tumour stage for tumours starting in the space around the eye (orbit):

T1 – The tumour is no greater than 2 centimetres in size.
T2 – The tumour is greater than 2 centimetres in size but has not grown into the bones surrounding the eye.
T3 – The tumour has grown into the bones surrounding the eye or other bones of the skull.
T4 – The tumour has grown into the eye (the globe) or the surrounding tissues such as the eyelids, sinuses, or brain.

If after microscopic examination, no tumour is seen in the resection specimen sent to pathology for examination, it is given the tumour sta,ge pT0, which means there is no evidence of a primary tumour.

If your pathologist cannot reliably evaluate the tumour size or the extent of growth, it is given the tumour stage pTX (primary tumour cannot be assessed).  This may happen if the tumour is received as multiple small fragments.

Nodal stage (pN) for angiosarcoma

Angiosarcoma is given a nodal stage between 0 and 1 based on the presence or absence of cancer cells in one or more lymph nodes.

If no cancer cells are seen in any lymph nodes, the nodal stage is N0. If no lymph nodes are sent for pathological examination, the nodal stage cannot be determined, and it is listed as NX. If cancer cells are found in any lymph nodes, the nodal stage is listed as N1.

About this article

Doctors wrote this article to help you read and understand your pathology report. If you have additional questions, contact us.

Other helpful resources

Atlas of Pathology