Phyllodes Tumors of the Breast

Phyllodes tumors (or phylloides tumors) are rare breast tumors that start in the connective (stromal) tissue of the breast, not the ducts or glands (which is where most breast cancers start). Most phyllodes tumors are benign and only a small number are malignant (cancer)

Phyllodes tumors are often divided into 3 groups, based on how they look under a microscope:

• Benign (non-cancerous) tumors account for more than half of all phyllodes tumors. These tumors are the least likely to grow quickly or to spread.
• Borderline tumors have features in between benign and malignant (cancerous) tumors.
• Malignant (cancerous) tumors account for about 1 in 4 phyllodes tumors. These tend to grow the fastest and are the most likely to spread or to come back after treatment.

Who is most at risk for phyllodes tumors?

Phyllodes tumors are most common in women in their 40s, but women of any age can have them. Women with Li-Fraumeni syndrome (a rare, inherited genetic condition) have an increased risk for phyllodes tumors.

Diagnosis of phyllodes tumors

Phyllodes tumors are usually felt as a firm, painless breast lump, but some may hurt. They tend to grow large fairly quickly, and they often stretch the skin.

Sometimes these tumors are seen first on an imaging test (like an ultrasound or mammogram), in which case they’re often hard to tell apart from fibroadenomas. 

The diagnosis can often be made with a core needle biopsy, but sometimes the entire tumor needs to be removed (during an excisional biopsy) to know for sure that it’s a phyllodes tumor, and whether it's malignant or not.

How do phyllodes tumors affect your risk for breast cancer?

Having a benign phyllodes tumor does not affect your breast cancer risk. If you have a malignant phyllodes tumor, it does not affect your risk of getting other types of breast cancer. Still, you may be watched more closely and get regular imaging tests after treatment for a phyllodes tumor, because these tumors can sometimes come back after surgery.

Treatment of phyllodes tumors

Phyllodes tumors typically need to be removed completely with surgery. 

If the tumor is found to be benign, an excisional biopsy might be all that is needed, as long as the tumor was removed completely.

If the tumor is borderline or malignant, a wider margin (area of normal tissue around the tumor) usually needs to be removed as well. This might be done with breast-conserving surgery (lumpectomy or partial mastectomy), in which part of the breast is removed. Or the entire breast might be removed with a mastectomy, especially if a margin of normal breast tissue can't be taken out with breast-conserving surgery. Radiation therapy might be given to the area after surgery, especially if it’s not clear that all of the tumor was removed.

Malignant phyllodes tumors are different from the more common types of breast cancer. They are less likely to respond to some of the treatments commonly used for breast cancer, such as the hormone therapy or chemotherapy drugs normally used for breast cancer. Phyllodes tumors that have spread to other parts of the body are often treated more like sarcomas (soft-tissue cancers) than breast cancers.

Phyllodes tumors can sometimes come back in the same place. Because of this, close follow-up with frequent breast exams and imaging tests are usually recommended after treatment.