[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Breast](https://durgical.com/en/general-pathology/areas/breast/) › Tumours of the intralobular stroma: fibroadenoma vs phyllodes tumour

# Tumours of the intralobular stroma: fibroadenoma vs phyllodes tumour

- Lesion

Both tumours grow from the stroma around the lobules. Fibroadenoma is the harmless lump of young women; phyllodes is larger, older and can recur or spread.

Updated Nov 12, 2026

## Key points

- Fibroadenoma: young women (twenties and thirties); well-circumscribed, rubbery, grey-white, mobile; stroma compresses ducts into slits.
- Stroma is clonal, with MED12 mutations in most fibroadenomas and many phyllodes tumours.
- Fibroadenomas may grow in pregnancy, infarct, and calcify after menopause; complex fibroadenomas (with cysts or sclerosing adenosis) carry a slight cancer risk.
- Phyllodes tumour: older (forties to sixties), often large and fast-growing; leaf-like fronds, increased stromal cellularity and stromal overgrowth.
- Grading by stromal cellularity, atypia, mitoses, overgrowth and border; malignant phyllodes spreads by blood (not lymph nodes), so axillary dissection is not needed.
- Treatment of phyllodes is excision with a margin to prevent local recurrence.

On this page

- The basics Key points
- What it is
- Structure
- Step by step
- Fibroadenoma vs phyllodes tumour
- Markers
- Memory aid
- Elsewhere in DurgiPedia

- Clinical Clinical notes

- Study Test yourself

- Connections Connections

## What it is

Fibroadenoma and phyllodes tumour are biphasic tumours in which the specialised stroma of the lobule proliferates and carries ducts along with it. Fibroadenoma is the commonest benign breast tumour, typical of young women: a mobile, rubbery, well-circumscribed lump that often carries MED12 mutations. Phyllodes tumour occurs a decade or more later, grows larger and faster, and has a more cellular stroma that pushes leaf-like fronds into cleft-like spaces. Phyllodes tumours are graded benign, borderline or malignant; they tend to recur locally, and malignant ones can spread through the blood.

## Structure

- Fibroadenoma: stroma surrounding ducts (pericanalicular) or pressing them into curved slits (intracanalicular), both with a two-layered epithelium.
- Phyllodes: club-like fronds of cellular stroma covered by epithelium, projecting into elongated spaces; stromal cells condense beneath the epithelium.
- Malignant phyllodes: stroma with marked atypia, many mitoses, overgrowth without epithelium and infiltrative borders; heterologous sarcoma may appear.

## Step by step

- A stromal cell of the lobule acquires a MED12 mutation.
- The clone proliferates under hormonal influence and drags ducts into the growing tumour (fibroadenoma).
- In phyllodes tumours, additional changes (TERT promoter and others in higher grades) make the stroma more cellular and autonomous.
- Malignant phyllodes stroma behaves like a sarcoma and can reach the lungs and bone through the blood.

## Fibroadenoma vs phyllodes tumour

| Feature | Fibroadenoma | Phyllodes tumour |
| --- | --- | --- |
| [Typical age](https://durgical.com/en/conditions/breast-fibroadenoma/) | Twenties and thirties | Forties to sixties |
| Size and growth | Usually small, slow | Often large, can grow rapidly |
| Architecture | Slit-like ducts in uniform stroma | Leaf-like fronds into cleft-like spaces |
| Stroma | Low cellularity, no atypia | Increased cellularity, atypia and mitoses vary with grade |
| Behaviour | Benign, rarely recurs | Local recurrence; malignant ones metastasise by blood |
| Treatment | Observation or simple excision | Excision with a clear margin |

## Markers

- CD34 and ER-beta in stroma (variable)
- Ki-67 (higher in phyllodes)
- MED12 and TERT promoter testing (research and difficult cases)

## Clinical notes

- A young woman with a mobile, painless, rubbery lump most likely has a fibroadenoma; imaging and a core biopsy confirm it.
- A rapidly growing fibroepithelial lump in an older woman suggests phyllodes tumour and needs wide excision.
- Multiple fibroadenomas can occur in women taking cyclosporine after transplantation.

## Memory aid

Fibroadenoma is a quiet marble; phyllodes is a book whose leaves keep growing.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the most common benign breast tumour in young women?

Fibroadenoma.

## How does a phyllodes tumour differ from a fibroadenoma under the microscope?

It has more cellular stroma with overgrowth and leaf-like fronds projecting into cleft-like spaces; atypia and mitoses increase with grade.

## Why is axillary dissection not done for malignant phyllodes tumour?

Its malignant stroma spreads by blood like a sarcoma, rarely to lymph nodes.

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## Elsewhere in DurgiPedia

- [Breast: ducts, lobules and changes with life stage](https://durgical.com/en/histology/breast-ducts-lobules-and-changes-with-life-stage/)

## Connections

## Related 5

- [Breast disease: presentations and developmental anomalies](https://durgical.com/en/general-pathology/breast-disease-presentations-and-developmental-anomalies/)
- [Interlobular stromal lesions and other breast malignancies](https://durgical.com/en/general-pathology/interlobular-stromal-lesions-and-other-breast-malignancies/)
- [Atypical breast hyperplasia and cancer risk](https://durgical.com/en/general-pathology/atypical-breast-hyperplasia-and-cancer-risk/)
- [Uterine leiomyoma](https://durgical.com/en/general-pathology/uterine-leiomyoma/)
- [Benign vs malignant tumours: the comparison table](https://durgical.com/en/general-pathology/benign-vs-malignant-tumours-the-comparison-table/)

## Related conditions 3

- [Breast fibroadenoma](https://durgical.com/en/conditions/breast-fibroadenoma/)
- [Soft tissue sarcomas (liposarcoma, leiomyosarcoma, rhabdomyosarcoma)](https://durgical.com/en/conditions/soft-tissue-sarcomas/)
- [Breast cancer](https://durgical.com/en/conditions/breast-cancer/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Fibrocystic Breast Disease](https://www.ncbi.nlm.nih.gov/books/NBK551609/) (StatPearls (NCBI Bookshelf), 2026); [Breast Cancer Treatment (PDQ®)–Health Professional Version](https://www.cancer.gov/types/breast/hp/breast-treatment-pdq) (National Cancer Institute, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/tumours-of-the-intralobular-stroma-fibroadenoma-vs-phyllodes-tumour/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/tumours-of-the-intralobular-stroma-fibroadenoma-vs-phyllodes-tumour/