Learn about your pathology report:

Angiosarcoma

What is angiosarcoma?

Angiosarcoma is a type of cancer that develops from the endothelial cells normally found on the inside of blood vessels. It is part of a group of cancers called sarcomas. Sarcomas are cancers that develop from mesenchymal tissues which include nerves, fat, muscle, blood vessels, tendons, ligaments, bone and cartilage. Most angiosarcomas occur in adults. The most common locations include the scalp, skin and soft tissue under the skin. Other body sites that can be affected include the breast, liver, lung and spleen.

angiosarcoma

Blood vessels

Blood vessels are found throughout our body. Blood vessels that carry blood away from the heart and to the body are called arteries and arterioles. Blood vessels that carry blood away from the body and back to the heart are called veins and venules. The inside of a blood vessel is lined by a specialized type of cell called an endothelial cell.

Risk factors

There are several risk factors that 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 swelling of tissues that can develop after the removal of lymph nodes. Finally, some angiosarcomas develop in an area that has previously been treated by radiation therapy.

Genetic changes

Angiosarcomas do not have any characteristic genetic changes that can be tested for at the present time. However, some angiosarcomas may have an increased number of copies of the MYC gene. Increased copies of the MYC gene are more common in angiosarcomas that develop from previous radiation therapy or chronic lymphedema.

How do pathologists make this diagnosis?

The first diagnosis of an angiosarcoma is usually made after a small sample of the tumour is removed in a procedure called a biopsy. The biopsy tissue is then sent to a pathologist who examines it under a microscope.

Immunohistochemistry is a test pathologists perform to see the proteins being made by cells in a tissue sample.  The tumour cells in angiosarcoma will be positive for blood vessel markers, such as CD34, CD31, FLI1, ERG and Factor VIII.

After a pathologist makes a diagnosis of angiosarcoma or suggests the diagnosis as a possibility, the patient is usually treated first with surgery to remove the tumour. Some patients may receive chemotherapy and/or radiation therapy before surgery. When the tumour is surgically removed as a resection specimen, it is sent to pathology for examination.

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 when compared to normal endothelial cells. Pathologists describe these cells as atypical. Dividing tumour cells called mitoses are usually also seen.

Histologic grade

Grade is a word pathologists use to describe how different the cancer cells look and behave compared to normal endothelial cells. The grade can only be determined after a sample of tumour has been examined under the microscope.

Usually, tumours that look high grade under the microscope have a worse prognosis than tumours that look low grade under the microscope. However, some types of sarcoma are not graded because research has shown that grade does not accurately predict how the tumour will behave.

Currently, there is debate whether angiosarcoma should be graded. Your pathologist may grade your angiosarcoma using an internationally recognized system created by the French Federation of Cancer Centers Sarcoma Group (FNCLCC) or may choose to not include a grade in your pathology report.

If your report includes a grade it will be based on the FNCLCC grading system. According to this system, your pathologist will look for three microscopic features when examining the tumour sample (see below). Points are given for each feature (from 0 to 3) and the total number of points determines the final grade of the tumour.

  • Tumour differentiation – Tumour differentiation describes how closely the cancer cells look like normal endothelial cells. Tumours that look very similar to normal endothelial cells are given 1 point while those that look very different from normal endothelial cells are given 2 or 3 points.
  • Mitotic count – A cell that is in the process of dividing to create two new cells is called a mitotic figure. Tumours that are growing fast tend to have more mitotic figures than tumours that are growing slowly. Your pathologist will determine the mitotic count by counting the number of mitotic figures in ten areas of the tumour while looking through the microscope. Tumours with no mitotic figure or very few mitotic figures are given 1 point while those with 10 to 20 mitotic figures are given 2 points and those with more than 20 mitotic figures are given 3 points.
  • NecrosisNecrosis is a type of cell death. Tumours that are growing fast tend to have more necrosis than tumours that are growing slowly. If your pathologist sees no necrosis, the tumour will be given 0 points. The tumour will be given 1 point if necrosis is seen but it makes up less than 50% of the tumour or 2 points if necrosis makes more than 50% of the tumour.

The final grade is based on the total number of points given to the tumour:

  • Grade 1 – 2 or 3 points.
  • Grade 2 – 4 or 5 points.
  • Grade 3 – 6 to 8 points.

Low grade sarcomas are grade 1.  High grade sarcomas have a grade of either 2 or 3.

What to look for in your report after the tumour has been removed

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. Tumours less than 5 cm are associated with a better prognosis.

Tumour extension​

Angiosarcomas can grow into or around organs and bone.  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.

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 tumour that is dead.

Perineural invasion

Nerves are like long wires made up of groups of cells called neurons. Nerves transmit information (such as temperature, pressure, and pain) between your brain and your body. Perineural invasion is a term pathologists use to describe cancer cells attached to a nerve.

perineural invasion

Perineural invasion is important because cancer cells that have attached to a nerve can use the nerve to travel into tissue outside of the original tumour. For this reason, perineural invasion is associated with a higher risk that the tumour will come back in the same area of the body (local recurrence) after treatment.

Lymphovascular invasion

Blood moves around the body through long thin tubes called blood vessels. Another type of fluid called lymph which contains waste and immune cells moves around the body through lymphatic channels.

lymphovascular invasion

Cancer cells can use blood vessels and lymphatics to travel away from the tumour to other parts of the body. The movement of cancer cells from the tumour to another part of the body is called metastasis. Before cancer cells can metastasize, they need to enter a blood vessel or lymphatic. This is called lymphovascular invasion.

Lymphovascular invasion is important because it increases the risk that cancer cells will be found in a lymph node or a distant part of the body such as the lungs.

Margins

A margin is any tissue that was cut by the surgeon to remove the tumour from your body.  Depending on the type of surgery you have had, the margins can include bones, muscles, blood vessels, and nerves that were cut to remove the tumour from your body.

Margin

All margins will be very closely examined under the microscope by your pathologist to determine the margin status. Specifically, a margin is called negative when there are no cancer cells at the edge of the cut tissue. A margin is called positive when there are cancer cells at the edge of the cut tissue. A positive margin is associated with a higher risk that the tumour will recur in the same site after treatment (local recurrence).

Lymph nodes​

Lymph nodes are small immune organs located throughout the body. Cancer cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour (see Lymphovascular invasion above). The movement of cancer cells from the tumour to a lymph node is called metastasis.

Lymph node

Many cancers can spread to the lymph nodes, but angiosarcoma does this very rarely. If lymph nodes were part of the surgery to remove your tumour, your pathologist will assess them under the microscope and report whether they are involved by tumour.

Pathologic stage

​The pathologic stage for angiosarcoma is based on the TNM staging system, an internationally recognized system originally 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 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 that surrounds the organ from which is 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 stage pT0 which means there is no evidence of 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 the nodal stage is listed as NX.  If cancer cells are found in any lymph nodes, then the nodal stage is listed as N1.

Metastasis stage (pM) for angiosarcoma

Angiosarcoma is given a metastatic stage of 0 or 1 based on the presence of cancer cells at a distant site in the body (for example the lungs). The metastatic stage can only be assigned if tissue from a distant site is submitted for pathological examination. Because this tissue is rarely present, the metastatic stage cannot be determined and is listed as MX.

The metastatic stage can only be given if tissue from a distant site is sent for pathological examination. Because this tissue is rarely present, the metastatic stage cannot be determined, and it is typically not included in your report.

by Bibianna Purgina, MD FRCPC (updated June 25, 2021)
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