Fibroadenoma


DEFINITION
A common benign cause of breast lump in young woman.
AKA adenofibroma.

D I A B M I M


INCIDENCE

Commonest breast tumour in women <30 (Sabiston).
Account for 60% of breast lumps in young women.
- only rarely seen as a new lump beyond 40 (Sabiston).

Risk Factors
Women on cyclosporin A after renal transplant (50%).
D I A B M I M


AETIOLOGY

Hyperplasia or benign neoplasm or both?
- no consistent cytogenetic changes have yet been found.
- some polyclonal, due to focal hyperplasia of lobular stroma
- others more clearly tumours of stromal cells.
--> the stromal element then is clonal, but the epithelial element polyclonal.

Also accepted as a generic term for other benign mixed-gland-mesenchymal tissue tumours of breast
- includes hamartomas, other adenomas,
D I A B M I M


BIOLOGICAL BEHAVIOUR

Pathology
Fibrous hamartomas.
- composed of stromal and epithelial elements.
Frequently multiple and bilateral.
- more often when due to drug-related stimulation.
Smooth, rubbery, may be lobulated.
- white cut surface with brown glandular areas possible.
Well encapsulated so easy to enucleate.
Hormonally-responsive epithelium.
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Histology

Usually delicate cellular stroma, resembles intralobular stroma
- enclose glandular and cystic spaces lined by epithelium
Variable proportion of epithelial and stromal proliferation.
- stroma may be cellular or replaced by acellular swirls of collagen.
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Closely related to phyllodes
Histologic definition between fibroadenoma and benign phyllodes is at-times tenuous.
- often large FAs with any suggestion of hypercellularity are termed phyllodes.
- there is no harm from this.
<5 mitoses / high powered field, mild stromal pleomorphism, and circumscribed margins.

Natural History
Usually appear in teenage girls / early reproductive years.
May enlarge cyclically, or with pregnancy or breastfeeding.
Usually cease growing at around 2-3cm (Bland)
Do not progress to cancer.
- but don't forget a cancer may arise amongst their epithelial elements.
- >100 case reports of this since 1985 (Sabiston)
- most of these LCIS, 35% infiltrating Ca, 15% intraductal Ca.
Cancer in a newly diagnosed fibroadenoma is exceedingly rare.

Giant fibroadenoma
Sometimes appear during puberty (B&L)
>5cm in diameter and grow rapidly.
- same in all other respects.

Do these women have an increased risk of cancer?
Risk not well defined.
- in one study only those 'complex' FAs with cysts >3mm, sclerosing adenosis, epithelial calcifications or papillary apocrine change conferred a mild increased risk.
Some have suggested a modest increase, at about 2x that of general population (Sabiston).
- ie only slightly higher than reported excess risk for all women who had undergone previous breast biopsy.
Have been found to have slight overall risk for later cancer (Bland) only if:
- adjacent epithelium has proliferative changes or those 'complex' changes identified above
Without these features, no added risk.

D I A B M I M


MANIFESTATIONS

Local
Firm, rubbery, round, smooth or bosselated, highly mobile lumps.
- may be lobulated
- but slip easily under the examining fingers.
May rarely be tender.
Often increases a little in size with menstrual cycle (hormonally responsive).
- may mimic a cancer during pregnancy
- and regresses after menopause.
Gradually increase in size over several months.
Occasionally a lymph reaction may mimic carcinoma.
D I A B M I M


INVESTIGATIONS

Identified by USS, core biopsy

Assess as per usual breast lump.
- needle exam reveals no fluid.
- mammogram cannot differentiate these from cysts.
- but USS will show a cyst's cavity.
- may have some calcification
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D I A B M I M


MANAGEMENT

Operative

Obtain a core biopsy
and watch.
- if the lesion is typically a fibroadenoma
- and if the woman is satisfied
--> leave it in the breast
- this is most appropriate  for up to 2-3cm lesions in pts <25yrs (Bland)
- acceptable for those 25-35 but not beyond.

Evidence-basis

A prospective trial has evaluated the safety of conservation (Bland)
- all <40yrs and triple assessment completed; 90% agreed to participate, 10% opted for OT
- if tumour volume increased 20%, it was excised (this occurred in 9%)
- pts were discharged at 2 years if the tumour remained static or regressed.
- no cancers developed.

Excision

Considered if:
- older than 35
-  increasing in size
- >2 or 3 cm
- tender
- or at patient's request.
Be as cosmetic as possible
- circumareolar incision preferred.
- modest tunneling as needed
- remove minimal adjacent breast tissue .
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REFERENCES
Sabiston 17th
Cotran 6th
Cameron 10th.
Bland. Diseases of the Breast. 3rd.