DEAR MAYO CLINIC:

Last month, I had a partial mastectomy for a high-grade malignant phyllodes tumor. I can find very little information about it. My oncologist said it's up to me if I want radiation, since it's only recently being used more frequently for this type of cancer. I want to be proactive to prevent a recurrence. What do you recommend?

ANSWER:

The best way to manage cancerous (malignant) phyllodes tumors remains controversial. This is an uncommon type of tumor with an unpredictable nature. The best course of action needs to be considered on an individual basis. Before you decide on further treatment, talk to an experienced radiation oncologist, preferably one at a medical facility where specialists from different areas can collaborate on your care.

Unlike more common types of breast tumors that start in milk ducts or milk-producing areas of the breast (lobules), phyllodes tumors begin in the breast's connective tissue. In most cases, these tumors are benign (not cancer) and can be removed with surgery. Rarely, though, as in your case, they are cancerous.

Historically, malignant phyllodes tumors have been treated by removing the entire breast (mastectomy). That's because they can be relatively large, and it's necessary to remove a margin of normal tissue around the tumor to reduce the chance that it will come back. After that much tissue has been removed, it can be difficult to preserve the breast's appearance in a way that's cosmetically acceptable to the patient.

Malignant phyllodes tumors tend to be limited to the breast tissue. If they return following treatment, it's often in the same breast. Collected data suggests that breast radiation following surgery for a malignant phyllodes tumor is beneficial when there's concern that a tumor could not be completely removed, or that not enough normal tissue could be taken from around the tumor. Some reports also suggest that radiation can reduce the risk of a tumor coming back whenever the surgery performed is less than a mastectomy. Under these circumstances, the general trend among radiation oncologists is to offer radiation for malignant phyllodes tumors.

Because these are rare tumors, most of the information available is based on retrospective data collected from clinical observations. Rigorous scientific research, in the form of a prospective randomized clinical trial, would be hard to conduct. So, without knowing all the details of your case, it's difficult to make specific recommendations. In addition to meeting with an experienced radiation oncologist to discuss the risks and benefits of radiation and to get an expert opinion regarding your situation, I would suggest you do two more things.

First, consider getting a second opinion on the tumor's classification. Phyllodes tumors have three classifications: benign, borderline and malignant. Because they are uncommon, the classification of these tumors may vary significantly from one pathologist to another. So, if you haven't already done so, it may be useful to have your pathology slides reviewed by an expert pathologist -- one who's seen a number of these tumors before -- to confirm the tumor's classification. This will impact treatment decisions and recommendations as you move forward.

Second, your medical oncologist should be familiar with the unpredictable nature of malignant phyllodes tumors. Although it's uncommon, these tumors can be very aggressive and (rarely) show up in other parts of the body outside of the breast. It's important that your follow-up care be managed by a specialist who's experienced in dealing with this type of tumor and follows you closely with appropriate tests.

Ideally, the pathologist, radiation oncologist and medical oncologist should be part of the same medical facility, so they can easily discuss your case and coordinate care, if need be.

Elizabeth Yan, M.D., Radiation Oncology, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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