Phyllodes (also spelled phylloides) tumors are rare breast tumors that, like fibroadenomas, contain 2 types of breast tissue – stromal (connective) tissue and glandular (lobule and duct) tissue. They are most common in women in their 30s and 40s (slightly older than for fibroadenomas), but they may be found at any age.
The tumors are usually felt as a painless lump, but some may be painful. They may grow quickly and stretch the skin. They are often hard to tell from fibroadenomas on imaging tests, or even with fine needle or core needle biopsies.
When seen under a microscope, the main difference between phyllodes tumors and fibroadenomas is that phyllodes tumors have an overgrowth of connective tissue. The cells that make up the connective tissue part can look abnormal under the microscope. Depending on how the cells look, phyllodes tumors may be classified as benign (non-cancerous), malignant (cancerous), or borderline (looking more abnormal than benign tumors, but not quite malignant). These types of tumors can behave differently.
Phyllodes tumors are usually benign but in rare cases may be cancerous. Less than 5% of these tumors spread to other areas, such as the lungs, or come back (recur) in distant areas after treatment. In the past, both benign and malignant phyllodes tumors were referred to as cystosarcoma phyllodes.
Phyllodes tumors (even benign ones) can sometimes come back in the same place if they are removed without taking some of the normal tissue around them. For this reason, they are treated by removing the mass and a 1 to 2 cm (about 1/2 to 3/4 inch) area of normal breast tissue from around the tumor.
Malignant phyllodes tumors are treated by removing them along with a wider margin of normal tissue, or by mastectomy (removing the entire breast) if needed. Malignant phyllodes tumors do not respond to hormone therapy and are less likely than most breast cancers to respond to chemotherapy or radiation therapy. Phyllodes tumors that have spread to distant areas are often treated more like sarcomas (soft-tissue cancers) than breast cancers.
Because these tumors can recur, close follow-up with frequent breast exams and imaging tests are usually recommended after treatment.
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