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Sidney Kimmel Cancer Center / Centers & Clinics

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Phyllodes Tumors

Phyllodes Tumors Diagnosis

Phyllodes (fil-oy-deez) tumors are a rare form of breast tumor; they can be benign (not cancerous), malignant (cancerous), or borderline (having characteristics of both).

Phyllodes tumors account for fewer than 1% of all breast cancers. Their unusual name comes from the Greek word for “leaf”, because they have a leaf-like appearance under the microscope.  Some inherited genetic disorders are known to increase the risk of developing a phyllodes tumor, but in most cases, the cause is unknown.

Most phyllodes tumors are benign.  They may look very much like common benign breast tumors called fibroadenomas. Often, the pathologist needs to look at the whole tumor under the microscope to make a diagnosis. This is why surgery to remove a phyllodes tumor is recommended, even if it is thought to be benign.  Unlike other kinds of benign breast lesions, benign phyllodes tumors can grow very quickly and become very large.

Malignant phyllodes tumors are a form of breast cancer; however, they are different from more common kinds of breast cancer. Unlike breast cancer which begins in the milk ducts, malignant phyllodes tumors begin in the connective tissue that surrounds and supports the ducts and lobules of the breast. Phyllodes tumors contain different kinds of cells, but the cancerous part is a sarcoma, or cancer of connective tissue. These tumor cells are very different than ductal breast cancer cells, and behave differently.

Phyllodes Tumor Staging and Treatment

Staging of malignant phyllodes is different from that of other types of breast cancer.  Lymph node status is not as important in staging these tumors as in other kinds of breast cancer.  This is because when sarcomas spread, they typically do not travel through the lymphatic system.  Even when sarcomas are very large tumors, lymph nodes are usually negative for cancer, and axillary lymph node dissection (removal of the lymph nodes under the arm) is often not necessary.

Treatment of malignant phyllodes tumors is also somewhat different than that of more common kinds of breast cancer. Phyllodes tumors that are only in the breast, whether benign or malignant, are most often treated with local therapy alone.  Only if the cancer is known to have spread to other parts of the body will systemic therapy be recommended.

Local therapy is aimed at preventing the tumor from coming back in the breast. Local therapy for a phyllodes tumor will include surgery (wide excision or mastectomy) to remove the tumor and extra tissue around it.  Sometimes, radiation is given as well. 

Systemic therapy (chemotherapy) may be used if a malignant phyllodes tumor has spread outside of the breast, though this not common.  Your oncology team will recommend a treatment plan based on what is known about malignant phyllodes tumors in general and specifically tailored to your disease.