Phyllodes tumors are a rare type of breast tumor, but they are not the same as breast cancer. They are relatively rare and usually benign, or noncancerous.

The pattern of phyllodes tumor cells resembles leaves, and the name “phyllodes” comes from the Greek word meaning “leaflike.” Phyllodes tumors account for less than 1% of all tumors. Although most are benign, around 10% are cancerous.

Females in their 40s and individuals with a rare inherited genetic condition called Li-Fraumeni syndrome are at an increased risk of phyllodes tumors. They are extremely rare in men.

This article looks at phyllodes tumors, their causes, symptoms, and diagnosis. It also covers potential treatment options.

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

A scan of a phyllodes tumor.Share on Pinterest
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Phyllodes tumors are rare tumors that begin in the breast’s connective tissue. They are different from breast cancer and are noncancerous in most cases. That said, around 10% are cancerous, while others are borderline, meaning they have features somewhere in between benign and malignant.

Phyllodes tumors can grow quickly, but they do not always spread beyond the breast. Although many of these tumors are benign, a doctor may recommend surgery to reduce the risk of further growth.

This kind of tumor can form at any age. However, they tend to affect females in their 40s. In younger females, they are more likely to be benign. They are rare in males.

Experts do not know the exact causes of phyllodes tumors. A hormone imbalance may play a role, and certain factors may increase a person’s risk, including:

Doctors do not fully understand how these factors interact to cause tumors. However, they think that a protein called endothelin-1 that stimulates breast fibroblast growth may contribute. Fibroblasts are cells that secrete collagen protein to create a structural framework in connective tissue.

The most common sign of a phyllodes tumor is a firm breast lump that is easy to feel and stretches the skin. These lumps often form in the upper outer portion of the breast. They can also make the veins distended, or swollen, so the breast appears blue or green.

The tumors tend to grow quickly and can range from 1–45 centimeters (cm) across. In some cases, they may affect the entire breast.

This type of tumor is not usually painful. Some people may notice a bloody nipple discharge, but nipple inversion and ulceration, or bloody sores, are uncommon.

Phyllodes tumors are rare, accounting for just 0.3 to 1% of all tumors. As a result, doctors may be less familiar with them, making diagnosis tricky.

It is also possible to mistake them for other growths. For example, a phyllodes tumor can look like a type of solid breast growth called a fibroadenoma. A fibroadenoma is a benign, growing lump of regular breast cells.

Fibroadenomas are the most common type of breast mass and often develop in younger females.

Some researchers have suggested that phyllodes tumors may be a type of fibroadenoma. However, there are two main differences between these types of tumors.

First, phyllodes tumors tend to grow more quickly than fibroadenomas. Second, phyllodes tumors tend to develop when people are in their 40s. Fibroadenomas usually appear earlier than this, when people are in their 20s and 30s.

These distinctions can help a doctor make an accurate diagnosis.

Imaging

As with other tumors, diagnosing a phyllodes tumor may involve a mammogram, MRI, or ultrasound.

The results of a mammogram will show a round mass with well-defined edges. In some cases, a tumor may have rounded lobes.

MRI or ultrasound imaging tests can give a more detailed picture of the breast tissue.

Learn more about what to expect during a mammogram.

Biopsy

Only a breast biopsy can confirm whether the mass is a phyllodes tumor.

A biopsy involves taking tissue samples for testing. These tests can confirm the type of tumor a person has.

If a doctor needs to test a tissue sample, they may recommend a core needle biopsy or an excisional biopsy. A core needle biopsy involves the doctor taking a sample through the skin using a hollow needle. However, this may not provide enough evidence that the mass is a phyllodes tumor.

An excisional biopsy involves a surgeon removing the whole tumor for testing. Examining the whole tumor can lead to a more accurate diagnosis.

Beyond confirming the type of tumor, a biopsy can help determine whether a tumor is benign, borderline, or malignant.

Identifying a tumor

Features of a benign tumor include:

  • well-defined edges
  • cells that do not divide rapidly
  • connective tissue cells that do not look unusual
  • no overgrowth of connective tissue cells

Features of a malignant tumor include:

  • irregular edges
  • cells that seem to be dividing rapidly
  • overgrown connective tissue cells with an unusual appearance

Borderline tumors have features of benign and malignant forms.

Malignant tumors, particularly those with lots of connective tissue overgrowth, may spread and grow quickly and extend beyond the breast.

The only way to treat a phyllodes tumor is to remove the growth entirely. This will prevent additional tumors from forming and stop the existing tumor from causing complications.

During the procedure, a surgeon will remove the tumor and at least 1 cm of surrounding tissue. This will reduce the chances of the tumor growing back.

If a person has a cancerous phyllodes tumor, a doctor will remove it just like a benign tumor. Because these tumors do not respond to hormone therapy, radiation and chemotherapy are unlikely to help.

Sometimes, if a cancerous phyllodes tumor comes back, a doctor may recommend a mastectomy. This is surgery to remove part or all of the breast.

Although benign phyllodes tumors may not spread beyond the breast, they need treatment to prevent them from growing larger. Otherwise, the lump can become visible and break through layers of skin, causing pain and discomfort.

Effect on cancer risk

If a malignant phyllodes tumor recurs, there is a limited risk of this type of tumor developing beyond the breast. Fewer than 5% of all phyllodes tumors recur elsewhere in the body.

Having a benign phyllodes tumor does not increase a person’s risk of developing cancer, including breast cancer.

After the removal of a phyllodes tumor, a person may experience pain at the site of the surgery. However, further complications are rare.

Benign phyllodes tumors are less likely to recur than malignant ones. A doctor will monitor a person to check for recurrence after removal.

The outlook for people with phyllodes tumors is generally good. People with malignant phyllode tumors have a 10-year survival rate of 87%.

According to a 2019 study that assessed people with phyllode tumors between 1957 and 2017, those who had a tumor that did not have poor features had a 10-year disease-specific survival rate of around 100%. The survival rate for those who had tumors that spread but did not recur was 94%.

Without treatment, however, even benign tumors can cause complications. For this reason, anyone who notices any breast changes should seek medical attention.

Although a person may feel concerned to receive the news they have a tumor, most phyllodes tumors are noncancerous.

Because these tumors are rare, doctors do not yet understand what causes them, but they think hormones play a role. Treatment involves surgically removing the tumor and having regular check-ups to ensure the tumor has not returned.