24th May 2025

Fibroadenoma

Fibroadenomas are the most common benign breast tumour, accounting for approximately 50% of all breast biopsies. They can affect women of any age, but are frequently seen in adolescent and young women between the ages of 15 and 35 years. Whilst they typically present as a solitary, unilateral breast lump, in 20% of cases, multiple fibroadenomas may manifest within the same breast or bilaterally.

The aetiology of these lesions remains unknown, however hormonal influences are thought to play a role due to their persistence during reproductive years and typical involution following menopause. Furthermore, changes in their size are often associated with pregnancy or in response to oestrogen therapy.  

Fibroadenomas classically present as a small (1-3cm in size), firm, painless and mobile mass with a smooth texture on clinical examination. Accompanying imaging is usually performed, with ultrasound being the preferred modality in younger women, due to dense breast tissue rendering mammography more challenging. Ultrasound and mammography usually reveal a well-defined, round to ovoid, hypoechoic lesion with smooth margins. Involutional change, typically seen in older, postmenopausal women, may also show characteristic ‘Popcorn calcifications’ on x-ray. 

In cases where there is diagnostic uncertainty, further investigation may be warranted by way of core biopsy or fine needle aspiration (FNA). This may include an enlarging lesion, atypical findings on imaging, a lesion >2.5cm in size or for ‘peace of mind’ for the patient. Histologically, fibroadenomas appear as a biphasic lesion comprising proliferation of both glandular and stromal tissue.

The majority of fibroadenomas do not carry an increased risk of breast cancer and therefore, most patients require no treatment or follow-up. However, surgical excision can be performed if the lesion is particularly large, or at the patient’s request.