What Is Metastatic Breast Angiosarcoma?

Breast angiosarcoma is already one of the rarest forms of breast cancer. When this disease becomes metastatic, meaning it has spread beyond the breast to other organs or tissues in the body, it presents an even more serious medical situation. While angiosarcoma can develop anywhere in the body, breast angiosarcoma specifically begins in the blood vessels or lymph vessels within breast tissue.^[1]

The disease is so uncommon that for every 1 million people in the United States, only one person will be diagnosed with angiosarcoma each year. This rarity means that researchers are still working to understand the best ways to prevent the cancer from spreading or returning after treatment.^[1]

When breast angiosarcoma becomes metastatic, cancer cells have traveled from the breast to distant parts of the body. Research shows that metastatic disease at presentation occurs in 16 to 44 percent of angiosarcoma cases, with overall survival ranging from 6 to 16 months in these advanced situations.^[7]

Epidemiology

Understanding who gets metastatic breast angiosarcoma helps paint a picture of this rare disease. Angiosarcoma makes up less than 2 percent of all soft tissue sarcomas in humans and primarily affects adults and elderly patients.^[7]

There are two main types of breast angiosarcoma, and they affect different age groups. Primary breast angiosarcoma, which occurs in people who have never had breast cancer before, most commonly develops when people are in their 30s and 40s. Secondary breast angiosarcoma, which develops after previous breast cancer treatment, tends to appear later in life, typically 7 to 10 years after radiation therapy.^[1]

The disease shows a similar distribution between males and females overall, though breast angiosarcoma naturally affects more women given its location.^[7]

For people who have received radiation therapy for breast cancer, the risk of developing angiosarcoma is higher than in the general population. A 2019 report estimated that 1 in 1,000 people who had radiation for breast cancer later developed angiosarcoma in the breast or chest wall. While this risk remains relatively low, awareness is important for anyone who has undergone radiation treatment.^[1]

Causes

The exact causes of primary breast angiosarcoma are not fully understood, which is largely due to how rare this cancer is. Scientists continue to study what triggers the transformation of normal blood vessel or lymph vessel cells into cancerous ones.^[1]

For secondary breast angiosarcoma, the causes are better understood. This form of the disease occurs in people who have previously been treated for breast cancer. Radiation therapy stands out as a significant factor in the development of secondary angiosarcoma. The cancer-causing effects of radiation can damage cells years after treatment has ended.^[1]

Beyond radiation, other definite risk factors for angiosarcoma in general include chronic lymphedema (long-term swelling), environmental carcinogens such as vinyl chloride, thorium dioxide, and arsenic, as well as certain genetic syndromes.^[7]

Some research suggests that removal of lymph nodes during breast cancer surgery, combined with chronic lymphedema in the breast or arm, may also increase the risk of developing breast angiosarcoma.^[1]

In rare cases, angiosarcoma has been associated with pregnancy. One documented case described a 36-year-old woman who presented with a progressive breast lump during the third trimester of her pregnancy and was subsequently diagnosed with angiosarcoma.^[5]

Risk Factors

Certain groups of people face higher risks of developing breast angiosarcoma. Anyone who has undergone radiation therapy for breast cancer should be aware of this potential long-term complication. The risk becomes relevant years after treatment, with secondary angiosarcoma typically appearing 7 to 10 years after radiation exposure.^[1]

People who have had lymph nodes removed as part of breast cancer treatment may face increased risk, especially if they develop chronic swelling in the breast or arm area afterward. This persistent swelling, known as lymphedema, creates conditions that may contribute to the development of angiosarcoma.^[1]

Age also plays a role in risk. For primary breast angiosarcoma, people in their 30s and 40s are most commonly affected. For secondary forms related to previous cancer treatment, the disease tends to appear in older individuals who received radiation therapy years earlier.^[1]

Symptoms

The symptoms of breast angiosarcoma can vary depending on whether it’s primary or secondary, and recognizing these signs early is crucial. Unfortunately, the symptoms can sometimes be mistaken for less serious conditions, which may lead to delays in diagnosis.^[1]

Primary breast angiosarcoma often presents with a thickened area of skin on the breast or a lump within the breast tissue. People may also notice a discolored rash or bruised appearance on the skin of the breast or arm. These visible changes are important warning signs that should prompt immediate medical attention.^[1]

Secondary breast angiosarcoma can appear differently. Many people with this form develop swelling in the breast or arm, along with lumps or skin changes. The disease may show up as what looks like a skin tag, pimple, or a purple or blue-colored spot on the breast. Because these appearances can seem minor or skin-related, people often first visit a dermatologist rather than their cancer doctor. This can lead to delays in getting the correct diagnosis, as the symptoms don’t immediately suggest cancer.^[1]

When angiosarcoma becomes metastatic, meaning it has spread to other parts of the body, additional symptoms may develop depending on where the cancer has traveled. One documented case described a patient who developed progressive abdominal swelling, leg swelling, jaundice (yellowing of the skin), and difficulty breathing after the cancer spread. These symptoms reflected metastasis to the liver and other organs.^[5]

Any breast lump, persistent pimple-like lesion, or bruise on the breast that doesn’t go away within a reasonable time should be evaluated by a doctor. These seemingly minor changes could be the first sign of something more serious.^[1]

Prevention

Preventing metastatic breast angiosarcoma is challenging because the disease is so rare and its causes are not completely understood. However, there are some measures that may help reduce risk, particularly for people who have been treated for breast cancer.

For those receiving radiation therapy for breast cancer, awareness represents a key form of prevention. While the overall risk of developing angiosarcoma after radiation remains low, knowing about this possibility allows people to watch for warning signs and seek medical attention quickly if symptoms appear. Early detection of angiosarcoma before it becomes metastatic offers the best chance for successful treatment.^[1]

Managing lymphedema effectively may also play a role in reducing risk. Since chronic swelling has been suggested as a potential risk factor, people who develop lymphedema after breast cancer treatment should work with their healthcare team to control this condition. This might include wearing compression garments, performing specific exercises, and receiving specialized massage therapy.

Regular follow-up care after breast cancer treatment is essential. People who have received radiation therapy should maintain contact with their cancer care team and report any unusual changes in their breast or chest area immediately. These check-ups allow doctors to monitor for late effects of treatment, including rare complications like angiosarcoma.^[1]

Unfortunately, for primary breast angiosarcoma that occurs without any previous cancer diagnosis, there are no known specific prevention strategies because the causes remain unclear.^[1]

Pathophysiology

Understanding what happens in the body when breast angiosarcoma develops and spreads helps explain why this disease is so aggressive. Angiosarcoma originates from the cells that line blood vessels or lymph vessels, called endothelial cells. These cells normally form a protective barrier inside vessels and help regulate the movement of substances in and out of the bloodstream or lymph system.^[7]

In angiosarcoma, these endothelial cells undergo abnormal changes that cause them to grow and divide uncontrollably. The resulting tumor is highly malignant, meaning it has a strong tendency to invade nearby tissues and spread to distant parts of the body. This aggressive behavior sets angiosarcoma apart from many other types of cancer.^[7]

Angiosarcoma is easily infiltrative, meaning it doesn’t stay neatly contained within one area but instead spreads into surrounding tissues. This characteristic makes it difficult to remove completely with surgery and contributes to high rates of local recurrence, even after treatment.^[7]

When angiosarcoma becomes metastatic, cancer cells break away from the original tumor in the breast and travel through the bloodstream or lymphatic system to other organs. The most common sites where breast angiosarcoma spreads include the lungs, bones, soft tissues, and skin. The liver can also be affected. One case documented multiple nodules in the liver when a patient’s angiosarcoma had metastasized.^[5]

There’s a specific type called epithelioid angiosarcoma, where the cancer cells have a predominantly rounded appearance rather than the typical elongated shape. This subtype is particularly aggressive and often presents with early spread to lymph nodes and other organs, especially the lungs, bones, soft tissue, and skin. Because epithelioid angiosarcomas can spread through both blood and lymph vessels, they’re more likely to reach lymph nodes compared to the standard form of the disease.^[10]

The molecular pathways involved in angiosarcoma development have not been fully described, though researchers have detected some gene mutations and altered protein expression levels in these tumors. Understanding these changes at the cellular level remains an active area of research that may eventually lead to more targeted treatment approaches.^[10]

One case study highlighted just how rapidly this disease can progress. A woman who was receiving adjuvant chemotherapy after surgery for breast angiosarcoma developed widespread metastatic disease within just 15 days of starting treatment. She presented with abdominal swelling, leg swelling, jaundice, and breathing difficulty. Scans revealed fluid around her lung, multiple liver nodules, and deposits in her lungs and skin—all signs that the cancer had spread aggressively despite ongoing treatment.^[5]