What Are Phyllodes Tumors? Understanding This Rare Type of Breast Tumor in Beverly Hills

A phyllodes tumor is a rare breast tumor that develops from the breast's connective tissue, also called stromal tissue, rather than the ducts or lobules where most breast cancers begin. They are most often diagnosed in women between the ages of 35 and 55, although they can occur at any age.

One reason phyllodes tumors can be difficult to diagnose is that they often resemble fibroadenomas, which are much more common benign breast tumors. On a physical exam or even on imaging, the two can appear very similar. According to the Cleveland Clinic, “it usually takes a biopsy to distinguish a phyllodes tumor from a fibroadenoma.” These biopsies include removing a small sample of breast tissue for laboratory testing. While there are various types of biopsies, the core-needle and surgical biopsy are most commonly used in breast biopsy procedures.

The answer depends on the type of phyllodes tumor. Unlike typical breast cancer, phyllodes tumors are classified into three categories based on how the cells appear under a microscope.

• Benign phyllodes tumors

This is the most common type, accounting for approximately 60 to 75 percent of cases.

Although benign phyllodes tumors are not cancerous, they are often still treated surgically because they can continue to grow quickly and may return if they are not completely removed.

• Borderline phyllodes tumors

Borderline phyllodes tumors have characteristics that fall between benign and malignant tumors. They are more likely to recur than benign tumors, making complete surgical removal with clear margins especially important.

• Malignant phyllodes tumors

Malignant phyllodes tumors are the rarest type, and occur in about 1 in 4 cases, according to The American Cancer Society. Unlike benign and borderline tumors, malignant phyllodes tumors are considered cancerous, and arise from connective tissue rather than breast glandular tissue. Complete removal is often recommended, and our team provides ongoing follow-up care to ensure optimal healing and monitor for recurrence. 

At Bedford Breast Center, we use a comprehensive, multidisciplinary approach to evaluate breast masses. Our specialists use a combination of clinical expertise, advanced breast imaging, and tissue sampling when appropriate to arrive at the most accurate diagnosis. Evaluation for breast masses, including phyllodes tumors, typically includes:

Breast Imaging

Depending on your age and clinical presentation, imaging may include:

• Diagnostic mammography
• Breast Ultrasound
• Vera Scan Breast CT

Core Needle Biopsy

If imaging findings suggest a phyllodes tumor, a core needle biopsy is typically performed to obtain small tissue samples for evaluation by a pathologist. While the biopsy often provides enough information to guide treatment, only a portion of the tumor is examined.

After the whole tumor is surgically removed, the entire specimen is sent for a comprehensive pathological examination. Evaluating the complete specimen allows the pathologist to assess the tumor's overall architecture, cellular features, margins, and other characteristics that are necessary to establish a definitive diagnosis and determine whether the tumor was benign, borderline, or malignant.

Breast-Conserving Surgery, also known as a Lumpectomy , is the primary treatment for all phyllodes tumors. Unlike many benign breast lumps that can simply be monitored, phyllodes tumors are generally removed because of their tendency to enlarge and recur. The goal of surgery is not only to remove the tumor itself but also to remove a surrounding rim of healthy tissue, known as a clear surgical margin. Obtaining clear margins significantly reduces the chance that the tumor will return.

The extent of surgery depends on several factors, including:

• The size of the tumor
• Whether clear margins can be achieved while preserving the breast
  • For very large tumors, more extensive surgery, including mastectomy, may be recommended, though breast-conserving surgery remains an option for many patients.

Yes. Even benign phyllodes tumors can recur if they are not completely removed. The likelihood of recurrence depends on several factors, including:

• Whether the tumor was benign, borderline, or malignant
• Whether clear surgical margins were achieved
• Whether the tumor has recurred previously

For this reason, patients are typically followed with regular breast examinations and imaging after surgery.

Because these tumors often look alike, patients frequently ask how they differ.

Fibroadenomas are among the most common benign breast tumors, particularly in younger women. They usually grow slowly and often do not require surgery unless they become symptomatic or enlarge significantly.

Phyllodes tumors, while sometimes appearing very similar on imaging, have a greater tendency to grow rapidly and recur. This is why physicians often recommend surgical removal once a phyllodes tumor is suspected or confirmed. Making the correct diagnosis is essential because treatment recommendations are different.

Many breast lumps ultimately prove to be benign, but no new breast mass should be ignored. You should schedule an evaluation if you notice:

• A new breast lump
• A lump that is increasing in size
• Persistent breast pain in one area
• Skin changes over the breast
• Changes in breast shape or contour
• Any breast symptom that does not resolve

Prompt evaluation allows your care team to determine whether the finding is benign, whether additional imaging is needed, or whether a biopsy should be performed.

At Bedford Breast Center, our multidisciplinary team combines advanced breast imaging, expert pathology, and specialized breast surgery to accurately diagnose and treat both common and rare breast conditions.

Whether your breast lump turns out to be a simple cyst, a fibroadenoma, or a phyllodes tumor, our goal is the same: provide an accurate diagnosis, develop the right treatment plan, and guide you through every step with expertise and compassion.

Do phyllodes tumors require chemotherapy?

Unlike common forms of breast cancer, chemotherapy and hormone therapy generally do not play a routine role in treating phyllodes tumors. The current recommendations for treatment of phyllodes tumors, including those that are classified as benign, is surgical removal.

Are phyllodes tumors common?

No. Phyllodes tumors account for less than 1% of all breast tumors, making them a rare breast condition.

Do phyllodes tumors always need surgery?

In most cases, yes. Complete surgical removal with clear margins is the standard treatment because even benign tumors can continue growing or recur.

What are the key differences between a fibroadenoma and a phyllodes tumor?

While phyllodes tumors and fibroadenomas are structurally very similar, some key differences make accurate diagnosis essential. According to a 2013 study in the National Library of Medicine, key distinctions are that phyllodes tumors grow quickly, are more likely to return, and may metastasize. Fibroadenomas are benign and are generally safe to leave in place. Watch this video to hear from Dr. Richardson on some of the key differences.