Breast Care A-Z · Condition · FIBROADENOMA

Fibroadenoma

also: fibroadenoma of the breast, benign breast lump (fibroadenoma), FA · pronounced fy-broh-ad-en-OH-ma

A fibroadenoma is a common, benign (non-cancerous) breast lump made of glandular and fibrous tissue, most often found in younger women. You may have had a lump diagnosed as a fibroadenoma and want to know what that means, or be reading about possible causes of a lump you have just noticed.

Quick answers

Can a fibroadenoma turn into cancer?

A confirmed fibroadenoma does not turn into breast cancer. Population studies do show a very small increase in long-term breast cancer risk in women who have had multiple fibroadenomas with certain microscopic features, but for an individual fibroadenoma the answer is straightforward: it is benign and stays benign.

Should I have my fibroadenoma removed?

Most can simply be left alone. Removal is offered when a fibroadenoma is growing, larger than around 3 cm, painful, has unusual features on imaging, or where the patient prefers it removed. There is no clinical pressure to remove a small, asymptomatic, biopsy-confirmed fibroadenoma.

Will a fibroadenoma grow back if I have it removed?

Not in the same place — a completely removed fibroadenoma does not recur. However, some women have a tendency to develop new fibroadenomas elsewhere in the breast, which are managed individually as they appear.

BREASTORY ENCYCLOPEDIA · PLATE XXXVIII ONCOLOGY · BENIGN BREAST TUMOURS fibroadenoma benign biphasic breast tumour the most common benign breast tumour, arising from lobular stroma and epithelium FIG 01 structural anatomy · pathological types · natural history i pseudo-capsule ii stromal component iii epithelial glands iv normal tissue v mobile within breast PATHOLOGICAL TYPES Intracanalicular: Stroma compresses glands into elongated slits/clefts Pericanalicular: Glands maintain open lumen surrounded by stroma Both subtypes are benign NATURAL HISTORY BY AGE <30 yrs → watch and wait policy 30–40 yrs → USS ± core biopsy >40 yrs → triple assessment ~80% undergo spontaneous involution; regression common in younger women FIG 01 — Fibroadenoma structure · biphasic tumour showing pseudo-capsule, stroma, and compressed gland spaces FIG 02 simple vs complex fibroadenoma Simple Fibroadenoma Complex Fibroadenoma Feature Definition No concerning features ≥1 complex feature present Size Typically <3 cm May be larger Calcification Absent Coarse calcification Cysts Absent Cysts >3 mm Adenosis Absent Sclerosing adenosis Metaplasia Absent Apocrine/epithelial Malignant risk 1.48× relative risk ~3× relative risk Age Any, peak 15–35 yrs 35–55 yrs typically Management Conservative Excision considered Follow-up Annual USS if conservative Biopsy advised FIG 03 fibroadenoma vs phyllodes tumour Feature Fibroadenoma Phyllodes Tumour Age 15–35 peak 40–50 peak Size Typically <3 cm Often >3 cm, rapid growth Growth rate Slow Rapid Margins Well-defined May be lobulated Stroma Moderate cellularity Hypercellular Mitoses Absent or rare Present Recurrence Rare 20–30% (benign phyllodes) Malignant risk <1% 10–25% (malignant phyllodes) Treatment Conservative or excision Wide local excision FIG 04 management pipeline Management Pipeline 1 Lump palpated Patient or clinician 2 Triple assessment Clinical, imaging, 3 Imaging (USS) Ultrasound first-line 4 Core biopsy 14G core if needed 5 Diagnosis confirmed B2 = benign; 6 Conservative/surgical Watch or excise FIG 05 fibroadenoma variant tiles Simple FA No complex features; conservative management Complex FA Cysts, adenosis or apocrine change present Giant FA (>5cm) Rapid growth; excision usually recommended Juvenile FA Adolescents; fast growth; often excised Phyllodes Tumour Leaf-like stroma; wide excision required Hamartoma Well-defined; mixed tissue composition FIG 06 key statistics Most common benign lump in <35 years [1] 10–15% have multiple lesions present [2] <1% risk of malignant transformation [3] ~80% reduce in size spontaneously [4] FIG 07 references References 1. Dixon JM. Fibroadenoma. BMJ 2012;344:e2567. 2. Greenberg R et al. Management of breast fibroadenoma. J Gen Intern Med 1998. 3. NICE NG101. Early and locally advanced breast cancer 2023. 4. Cant PJ et al. Fibroadenoma regression. Breast 1995;4:123. 5. Dent DM, Cant PJ. Fibroadenoma. World J Surg 1989;13:706. Clinically authored by Dr Fiona Tsang-Wright , FRCS (Gen Surg) GMC 4549831 · ORCID 0000-0003-4801-026X
Visual Reference · Fibroadenoma
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Definition
A fibroadenoma is a smooth, firm, mobile, benign (non-cancerous) lump in the breast made of normal glandular and connective tissue, most common in women under 30 and not a precursor to breast cancer.

Common questions The questions patients ask first

Can a fibroadenoma turn into cancer?
A confirmed fibroadenoma does not turn into breast cancer1. Population studies do show a very small increase in long-term breast cancer risk in women who have had multiple fibroadenomas with certain microscopic features (complex fibroadenoma or coexisting proliferative changes), but for an individual simple fibroadenoma the answer is straightforward: it is benign and stays benign3.
Should I have my fibroadenoma removed?
Most can simply be left alone4. Removal is offered when a fibroadenoma is growing, larger than around 3 cm, painful, has unusual features on imaging, or where the patient prefers it removed4. There is no clinical pressure to remove a small, asymptomatic, biopsy-confirmed fibroadenoma2.
Will a fibroadenoma grow back if I have it removed?
Not in the same place — a completely removed fibroadenoma does not recur. However, some women have a tendency to develop new fibroadenomas elsewhere in the breast, which are managed individually as they appear.
Can I still breastfeed if I have a fibroadenoma?
Yes. Fibroadenomas are made of normal lobular and fibrous tissue and do not interfere with milk production or breastfeeding. They sometimes enlarge slightly during pregnancy, which is a hormonal effect and not a sign of anything wrong.

A fibroadenoma is a smooth, firm, mobile, benign (non-cancerous) lump in the breast made of normal glandular and connective tissue, most common in women under 30 and not a precursor to breast cancer.

Fibroadenomas are the most common solid breast lump in younger women. They are not cancer, do not turn into cancer, and most do not need any treatment. Removal is sometimes offered if a fibroadenoma is growing, large, painful, or for the patient’s preference.

Orientation Why you might be reading about this

You have probably had a lump diagnosed as a fibroadenoma and want to know what that means, or you are reading about possible causes of a lump you have just noticed. Either way, “fibroadenoma” is one of the most common and most reassuring answers a breast clinic gives, and this page explains what it is, how it is diagnosed, and what (if anything) usually needs to be done about it.

Related terms: Breast lump · Breast cyst · Core biopsy · Phyllodes tumour · Triple assessment · Breast ultrasound

Definition What a fibroadenoma is

A fibroadenoma is made up of the normal building blocks of breast tissue — glandular lobules (the structures that would produce milk during breastfeeding) and fibrous stroma (the supporting connective tissue) — clumped together into a defined lump1. Hormones drive their development, which is why they tend to appear in women in their teens, twenties, and thirties, and often grow modestly during pregnancy or with hormonal contraception.

On clinical examination, a typical fibroadenoma feels:

  • Smooth — like a marble or grape, with a clear edge.
  • Firm or rubbery — solid rather than fluid-filled.
  • Mobile — sliding easily within the surrounding breast tissue when pressed (often called the “breast mouse”).
  • Painless — most are not tender, though some are uncomfortable around the menstrual cycle.

These features are typical but not diagnostic — imaging and, where appropriate, a biopsy are needed to confirm the diagnosis. A lump that feels like a fibroadenoma cannot be assumed to be one without that work-up.

Diagnosis How a fibroadenoma is diagnosed

The standard diagnostic pathway is triple assessment — clinical examination, imaging (ultrasound, sometimes with mammogram in older patients), and tissue sampling where indicated2. On ultrasound a typical fibroadenoma appears as a well-defined, oval, dark lesion with a thin echogenic capsule.

Whether a biopsy is done depends on the imaging features and the patient’s age2:

  • Young patient with a classic small fibroadenoma on ultrasound — biopsy is often not needed; the diagnosis is usually clear from imaging and the lump can simply be monitored or left alone.
  • Larger or atypical-appearing lesion — a core biopsy is recommended to confirm the diagnosis and exclude a phyllodes tumour, which can look very similar to a fibroadenoma on imaging but needs surgical removal1. Core biopsy cannot always reliably separate a cellular fibroadenoma from phyllodes; a B3 (cellular fibroepithelial lesion) result usually prompts excision (VAE or surgical) for definitive diagnosis. Core biopsy cannot always reliably separate a cellular fibroadenoma from phyllodes; a B3 (cellular fibroepithelial lesion) result usually prompts excision (VAE or surgical) for definitive diagnosis.
  • Lesion in an older patient — biopsy threshold is lower, because new “fibroadenoma-like” lumps in older women have a slightly higher chance of being something else.

Natural history What usually happens to fibroadenomas over time

Most fibroadenomas behave in one of three ways4:

  • Stay roughly the same size for years, sometimes shrinking slowly after the menopause.
  • Slowly increase in size during the reproductive years, particularly in pregnancy.
  • Spontaneously regress — disappear on their own, particularly in younger patients.

Sustained, rapid growth is unusual for a typical fibroadenoma and is one reason a re-imaging or removal is sometimes offered4. Most women who have been told they have a fibroadenoma do not need ongoing routine follow-up after the initial diagnosis2.

At consultation What to discuss with your surgeon

If a fibroadenoma has been confirmed on biopsy, the conversation usually covers:

  • Whether the lump is large enough or symptomatic enough to warrant removal, or whether it can safely be left alone.
  • Whether the imaging features include anything that warrants closer follow-up.
  • Whether you have a personal preference about removal — for cosmetic reasons, for reassurance, or because you find the lump itself bothersome.

For biopsy-proven concordant fibroadenomas, vacuum-assisted excision (VAE) under ultrasound is an established UK alternative to open excision. For background on open excision, see the fibroadenoma excision page.

New fibroadenomas are usually assessed in a one-stop clinic visit.

Resources Further reading

Sources & guidance

Every figure on this page is anchored to a published source. Tap a number in the text or below to jump to the reference.

  1. reference text WHO Classification of Tumours Editorial Board. Breast Tumours. WHO Classification of Tumours, 5th edition, vol. 2. Lyon: International Agency for Research on Cancer. 2019 ;Fibroepithelial tumours: fibroadenoma https://tumourclassification.iarc.who.int/ Cited for: Fibroadenoma definition (biphasic fibroepithelial lesion of glandular and stromal elements); benign classification; relationship to phyllodes tumour.
  2. guidance Royal College of Surgeons / Association of Breast Surgery. Best Practice Diagnostic Guidelines for Patients Presenting with Breast Symptoms. London: ABS. 2010 ;Section: solid benign lumps https://associationofbreastsurgery.org.uk/professionals/information-hub/guidelines/2010/best-practice-diagnostic-guidelines-for-patients-presenting-with-breast-cancer-symptoms Cited for: UK pathway: triple assessment for solid breast lumps; biopsy thresholds by age and imaging features; conservative management of biopsy-confirmed fibroadenoma.
  3. cohort Dupont WD, Page DL, Parl FF, et al. Long-term risk of breast cancer in women with fibroadenoma. New England Journal of Medicine. 1994 ;331(1):10–15 doi:10.1056/NEJM199407073310103 Cited for: Long-term cancer risk in women with simple fibroadenoma is comparable to background population; modest increase only in complex fibroadenoma or those with adjacent proliferative changes.
  4. cohort Cant PJ, Madden MV, Coleman MG, Dent DM. Non-operative management of breast masses diagnosed as fibroadenoma. British Journal of Surgery. 1995 ;82(6):792–794 doi:10.1002/bjs.1800820624 Cited for: Safety of conservative management of biopsy-confirmed fibroadenoma; common natural history (stable, slowly enlarging, or regressing); thresholds (size, growth) commonly used to consider excision.