Phyllodes tumor: benign or malignant? | Dr Zeitoun

Consultations at the practice, 241 rue du Faubourg Saint-Honoré (Paris 8th), and at Clinique Hartmann (Neuilly-sur-Seine). Surgery takes place at Clinique Hartmann.

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— Key figures

Phyllodes tumour

< 1 %

of breast tumours (rare lesion)

≈ 70 %

are Grade 1 (benign) on pathology

20-25 %

are Grade 2 (borderline, intermediate)

5-10 %

are Grade 3 (malignant, rarer)

Section 01 · Understanding

Understanding the phyllodes tumour

Receiving a phyllodes tumour diagnosis can be unsettling. The word itself is intimidating. This page is here to explain what it really is, what comes next, and why — in most cases — there's no reason to panic.

A phyllodes tumour is a rare fibroepithelial tumour — fewer than 1% of breast tumours. It looks like a fibroadenoma, but stands apart through its ability to grow quickly and, in rare cases, to behave aggressively. The vast majority of phyllodes tumours — about 60 to 75% — are entirely benign.

Its name comes from the Greek phyllon, meaning "leaf" — a reference to the leaf-like architecture seen under the microscope. The older term "cystosarcoma phyllodes" has been abandoned because it is misleading: most of these tumours are neither cysts nor sarcomas.

My approach: walking you through this precise diagnosis, removing the tumour with adequate margins to prevent recurrence, and arranging a simple, reassuring follow-up. This is a codified surgery, now guided by the 2025–2026 SENORIF guidelines.

Section 02 · Diagnosis

How the diagnosis is made

The most frequent presenting feature is a breast mass that grows rapidly — sometimes over a few weeks. On palpation, it is firm, mobile, painless, with sharp contours: very similar to a fibroadenoma, but typically larger and in a slightly older woman (35 to 55 years).

The diagnosis is built in three key steps: mammography and ultrasound, MRI when needed, and tissue sampling. These are the investigations that establish the diagnosis and properly prepare the surgery. Below, you will find a simple guide to reading your own report.

Understanding your mammogram

Dense oval opacity with sharp or polylobulated margins. ACR/BI-RADS classification explained step by step.

3D mammography unit — 3D mammography unit.

Interpreting your breast ultrasound

Heterogeneous hypoechoic mass with cystic clefts — a relatively specific feature of phyllodes tumours.

Breast ultrasound machine — Breast ultrasound machine.

Diagnosis Essential

Arranging your biopsy

Core or vacuum-assisted biopsy under ultrasound: techniques, procedure, waiting times, reading the pathology report.

Read article →

Sterile core biopsy device next to its packaging — Sterile core biopsy device next to its packaging.

Reading your report

What will be on your report?

The report you receive after biopsy or surgery can look obscure. In reality, only three pieces of information really matter. Here's what to look for — and what I'll walk through with you, line by line, in consultation.

01

Which type of tumour?

The key term is "phyllodes tumour". This confirms we are dealing with that specific condition — and not breast cancer, which is an entirely different disease.

02

Which grade?

Grade I, II or III — the second key piece of information. It indicates how aggressive the tumour is and directly drives surgical strategy and follow-up intensity.

03

Are the margins clear?

After surgery, the report tells whether enough healthy tissue was removed around the tumour. This determines whether the excision is complete or whether re-excision should be considered.

Section 03 · Classification

Three grades, three management strategies

Not all phyllodes tumours are alike.

The World Health Organization (WHO) classification — reflected in the 2025–2026 SENORIF and Saint-Paul-de-Vence guidelines — distinguishes three grades, which simply describe how mild or aggressive the tumour looks under the microscope.

This classification is not merely academic: it directly drives surgical margin requirements, surveillance intensity, and any indication for adjuvant radiotherapy.

Grade I

Benign phyllodes

60 to 75% of cases

The most common and least aggressive form. Low recurrence risk with clear margins. The most reassuring scenario.

Grade II

Borderline phyllodes

15 to 25% of cases

An intermediate form, between benign and malignant. 10 mm margins recommended and slightly closer follow-up.

Grade III

Malignant phyllodes

10 to 25% of cases

The most aggressive form, but rare. Real but limited metastatic risk (< 5%), mostly pulmonary. 10 mm margins mandatory.

Section 04 · Surgery

Excision with clear margins

Treatment relies exclusively on surgery. Neither chemotherapy nor hormone therapy has shown benefit as first-line therapy — phyllodes are neither hormone-sensitive nor reliably chemosensitive. Radiotherapy may be discussed in a tumour board for selected borderline or malignant cases.

The principle is simple: remove the entire tumour en bloc, with a cuff of healthy tissue all around. The minimum margin recommended by SENORIF 2025–2026 is ≥1 mm for benign phyllodes and ≥10 mm for borderline and malignant phyllodes. This is what distinguishes phyllodes surgery from a simple fibroadenoma — where "shelling out" often suffices.

Surgical options are tailored to tumour size, breast volume, and grade.

Wide local excision

First-line option in the vast majority of cases — even for large tumours, with strict margin compliance.

Support bra and dressings after wide local excision — Support bra and dressings after wide local excision.

Mastectomy Selected cases

Mastectomy

Reserved for very large tumours, multiple recurrences or diffuse malignant phyllodes. Immediate reconstruction almost always feasible.

Grey support bra laid flat, with no person in the frame — Grey support bra laid flat, with no person in the frame.

Breast reconstruction

Immediate or delayed. With fewer oncological constraints than epithelial cancer, options are broad.

Silicone breast implant on its own, on a neutral background — Silicone breast implant on its own, on a neutral background.

Consultations at the practice, 241 rue du Faubourg Saint-Honoré (Paris 8th), and at Clinique Hartmann (Neuilly-sur-Seine). Surgery takes place at Clinique Hartmann.

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Section 05 · Surveillance

Follow-up tailored to your grade

There is no strict national protocol in France for phyllodes surveillance. The most recent European recommendations — notably those of the UK Association of Breast Surgery, 2025 — together with international practice converge toward a 5-year follow-up, with intensity tailored to the grade reported on pathology.

In practice, the higher the grade, the closer the surveillance. Here is how I organize it for each of the three situations.

D+15

Postoperative consultation

Review of the definitive pathology report. Confirmation of grade, margin status, and personalized follow-up plan. This is when we choose the cadence for the next five years together.
Grade I

Benign phyllodes — light follow-up

Yearly clinical examination for 5 years, complemented by an annual mammography and ultrasound. Beyond 5 years, we return to age-appropriate standard screening.
Grade II

Borderline phyllodes — closer follow-up

Clinical examination every 6 months for 2 years, then yearly up to 5 years. Annual mammography and ultrasound for 5 years.
Grade III

Malignant phyllodes — close follow-up with chest imaging

Clinical examination every 6 months for 2 years, then yearly up to 5 years. Annual mammography and ultrasound for 5 years.

Your questions

Frequently asked questions about phyllodes tumours

The questions patients most often ask — before surgery, after, or simply to understand.

Is a phyllodes tumour cancer?▾

The vast majority of phyllodes tumours are benign. The WHO classification distinguishes three grades — Grade I (benign), Grade II (borderline) and Grade III (malignant). Only malignant forms (10 to 25% of cases) can metastasize, mainly to the lungs. For most patients, this is an isolated surgical episode with no long-term consequences.

How can a phyllodes tumour be distinguished from a fibroadenoma?▾

The differential diagnosis can be subtle, even on core biopsy. Rapid growth, size greater than 3 cm in a woman over 35, or a suggestive ultrasound pattern (intratumoral cystic clefts) point toward phyllodes. Confirmation is always histological, on the complete surgical specimen. More on fibroadenoma →

Why do clear margins matter so much?▾

Phyllodes tumours carry a recurrence risk directly tied to surgical margin status. A margin ≥1 mm for benign and ≥10 mm for borderline-malignant — per SENORIF 2025-2026 — significantly reduces this risk. This is why simple "shelling out", often sufficient for a fibroadenoma, is inadequate for a phyllodes tumour.

Should the axillary lymph nodes be removed?▾

No. Unlike breast cancer, phyllodes tumours — even malignant ones — almost never spread through the lymphatic system. Sentinel lymph node biopsy and axillary dissection are not indicated, except in case of a clinically palpable suspicious axillary node.

Can a phyllodes tumour recur?▾

Yes, recurrence is possible at all grades but stays low (5 to 10%) when excision is complete with clear margins. It rises to 15-25% for borderline and 20-30% for malignant. Close clinical and ultrasound surveillance during the first 2 years is therefore essential.

Is chemotherapy or hormone therapy needed?▾

Not as first-line therapy. Phyllodes tumours are neither hormone-sensitive nor reliably chemosensitive. Radiotherapy may be discussed in a tumour board for selected borderline or malignant cases excised with close margins — a collegial decision, never automatic.

Can I have a pregnancy after a phyllodes tumour?▾

Yes, with no restriction for the vast majority of patients. No contraindication to a future pregnancy or to hormonal contraception is supported by current guidelines. Phyllodes tumours are not hormone-sensitive.

How long is the hospital stay?▾

Phyllodes tumour excision is most often performed as day surgery — you go home the same day. For very large tumours or in case of mastectomy, 1 to 2 nights may be required.

What happens if margins are not clear?▾

If the histological analysis shows insufficient margins for the given grade, a re-excision is generally proposed. This decision is made at the day-15 consultation, in light of the definitive report and — when needed — a tumour board.

Can I request a second opinion?▾

Yes, and it is encouraged — especially since phyllodes grading can vary between laboratories. Expert pathology review and a thorough surgical opinion are valuable. Bringing your biopsy report and imaging is enough.

Sources & guidelines

Reference guidelines

SENORIF 2025-2026 — French breast cancer network guidelines for phyllodes tumour management, including margin recommendations and surveillance.
UK Association of Breast Surgery (ABS) — Contemporary management of phyllodes tumours of the breast. British Journal of Surgery, 2024.
WHO Classification of Breast Tumours — 5th edition. Histopathology, IARC, Lyon.
Tan BY, et al. Phyllodes tumours of the breast: a consensus review. Histopathology, 2016 Jan;68(1):5-21.
NCCN Guidelines — National Comprehensive Cancer Network. Breast Cancer treatment guidelines, including phyllodes tumour management.
INCa — French National Cancer Institute (Institut National du Cancer). Reference pathways for breast tumours.

Consultations at the practice, 241 rue du Faubourg Saint-Honoré (Paris 8th), and at Clinique Hartmann (Neuilly-sur-Seine). Surgery takes place at Clinique Hartmann.

Book on Doctolib → Request a call →

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