Phyllodes Tumor of the Breast

What a phyllodes tumor is

The breast contains glandular tissue (lobules and ducts) surrounded by supportive connective tissue called stroma. Most breast cancers start in the glandular cells. A phyllodes tumor starts mainly in the stroma, with both stromal and glandular elements. Under the microscope, overgrown stroma pushes into the ducts in a pattern that looks like leaves, which is where the name comes from (phyllodes is Greek for leaf-like).

Phyllodes tumors are related to fibroadenomas, the common benign breast lumps, but the stroma is more active and cellular. The old name cystosarcoma phyllodes is misleading, because most are neither cystic nor sarcomas, and it is no longer used.

The cause is unknown. Most occur without any risk factor. They are more common in people with Li-Fraumeni syndrome, an inherited TP53 gene change.

Grades of phyllodes tumor

The tumor is graded by a pathologist after it has been removed, based on how crowded and abnormal the stromal cells are, how fast they divide, the tumor's border and whether stroma overgrows the glandular parts.

Even benign phyllodes tumors need surgical removal because of their tendency to grow and recur.

Symptoms

• a smooth, firm, rounded lump that moves under the skin, usually painless
• rapid growth over weeks to months, often the feature that raises suspicion
• the lump can become large, sometimes over 10 cm, and change the shape of the breast
• stretched, shiny or bluish skin with visible veins over a large tumor
• rarely, skin ulceration from pressure, which does not by itself mean the tumor is malignant

Nipple changes and lymph node swelling are uncommon. Swollen armpit nodes, when present, are usually reactive rather than due to spread.

Phyllodes tumor vs fibroadenoma

They can look alike on imaging and even on a core biopsy, so a growing "fibroadenoma" is usually removed for full examination.

Diagnosis

• Clinical breast exam.
• Imaging: an ultrasound shows a solid, well-defined mass, sometimes with fluid spaces. A mammogram shows a smooth, round or lobulated mass. Neither can reliably tell it from a fibroadenoma.
• Core needle biopsy: removes small tissue samples. It can suggest a phyllodes tumor, but the final grade often requires the whole tumor. Fine needle aspiration is not reliable for this diagnosis.
• Excisional biopsy: removing the entire lump is often both the diagnosis and the treatment.
• Staging scans such as chest CT are done for malignant tumors to check for spread.

Treatment

Surgery

Surgical removal is the main treatment for all grades:

• Wide local excision (lumpectomy): removes the tumor with a rim of normal tissue. For borderline and malignant tumors, a margin of about 1 cm is generally recommended. For benign tumors, current guidelines accept excision with clear margins, without needing a wide margin.
• Mastectomy: used when the tumor is very large relative to the breast, or clear margins cannot be achieved with a lumpectomy. Breast reconstruction is possible.
• Re-excision: if the margins are not clear on the first operation, more surgery may be advised, especially for borderline and malignant tumors.

Because phyllodes tumors rarely spread to lymph nodes, the armpit nodes are not routinely removed, unlike in breast cancer.

Radiation therapy

Radiation after surgery may be recommended for malignant tumors, and sometimes borderline tumors, particularly when margins are close or the tumor is large, to reduce local recurrence.

Chemotherapy and hormone therapy

Hormone therapies used for breast cancer, such as tamoxifen, do not work for phyllodes tumors. Chemotherapy has a limited role and is used mainly for malignant tumors that have spread, often following sarcoma treatment approaches.

Recurrence and follow-up

Phyllodes tumors can come back in the same breast, usually within the first 2 to 3 years. Recurrence rates rise with grade and are higher when margins were not clear. A recurrence is usually treated with further surgery. Follow-up typically includes a breast exam every 6 months for a few years and yearly imaging, with chest imaging for malignant tumors.

Outlook

The outlook for benign and borderline phyllodes tumors is excellent once they are completely removed. Malignant phyllodes tumors are more serious. Most are cured by surgery with clear margins, but a minority spread to the lungs or bones, where they are difficult to treat. Across all grades, the chance of distant spread is low.

Frequently asked questions

Is a phyllodes tumor cancer?

Most are not. About 60% to 75% are benign and do not spread. Borderline tumors sit in between, and about 10% to 20% are malignant, meaning they can spread to other parts of the body. All grades are removed surgically because they can grow and recur.

How fast does a phyllodes tumor grow?

Phyllodes tumors often grow noticeably over weeks to months, which is one of the main features that separates them from fibroadenomas. Some reach more than 10 cm. Any breast lump that is enlarging should be checked promptly.

What is the difference between a phyllodes tumor and a fibroadenoma?

Both are firm, smooth breast lumps from the same tissue type. Fibroadenomas are common, appear in younger women, grow slowly and are benign. Phyllodes tumors are rare, occur in older women, grow faster, recur after removal and can occasionally be malignant.

Can a phyllodes tumor come back after surgery?

Yes. Local recurrence is the main risk, especially for borderline and malignant tumors or when margins were not clear. Most recurrences appear within 2 to 3 years and are treated with further surgery, sometimes followed by radiation.

Do phyllodes tumors spread to the lymph nodes?

Rarely. Unlike typical breast cancers, malignant phyllodes tumors spread mainly through the bloodstream to the lungs and bones. That is why lymph node surgery in the armpit is not usually part of treatment.