It is a benign encapsulated tumour occurring commonly in young females of 15–25 years age group—older definition. Presently, it is considered as hyperplasia of a single lobule of the breast (classified under ANDI).
It is the most common benign tumour of the breast below 30 years of age in females. It is aberration in normal development (AND) of a lobule.
It shows similar hormonal activities of normal breast like lactation, perimenopausal involution.
Incidence is 15% of palpable breast lumps. It is common in blacks and Negroes.
It is bilateral in 20% of cases. 20% are multiple.
Juvenile fibroadenoma occurs in adolescent girls, rarely (variant). Even though it shows rapid growth with stromal and epithelial hyperplasia, it does not show any alteration in stromal epithelial balance or cellular atypia or periductal cellular concentration. It may clinically mimic phyllodes tumour. But it does not turn into phyllodes tumour or carcinoma.
Complex fibroadenoma (Dupon et al) is a condition (variant) having typical fibroadenoma with fibrocystic changes like apocrine metaplasia, cyst formation, sclerosing adenosis. 15% of proven fibroadenomas are complex. It occurs in older age group. Occasionally it may turn into malignancy unlike usual fibroadenomas. Core biopsy is needed to confirm the condition.
30% of fibroadenomas may disappear or reduce in size in 2–4 years.
10–15% will increase in size progressively. It does not occur after menopause unless women are on hormones.
Fibroadenoma does not turn into malignancy.