Breast lumps are a common presenting complaint and fortunately the majority of which are benign. Naturally, breast lumps will often cause anxiety amongst patients due to risk over malignancy; importantly, any lump that is not certain to be benign, should be examined, imaged, and biopsied as appropriate.

Types of Benign Tumours

Fibroadenoma

Fibroadenoma is the most common benign growth in the breast and usually occurs in women of a reproductive age. They are proliferations of stromal and epithelial tissue of the duct lobules.

On examination, they are highly mobile lesions (historically termed a “breast mouse”) that are well-defined and rubbery on palpation, with most less than 5cm in diameter. They can be multiple and bilateral.

They have a very low malignant potential and can be left in situ with routine follow up appointments; over a 2 year period, up to 30% will get smaller. The main indications for potential excision are >3cm in diameter or patient preference.

Adenoma

A ductal adenoma is a benign glandular tumour, typically occurring in the older female population. The lesions themselves are nodular and can easily mimic malignancy, therefore most cases will undergo escalation for triple assessment.

Papilloma

Intraductal papillomas are a benign breast lesion that usually occur in females in their 40-50yrs, most typically occurring in the subareolar region (usually less than 1cm away from the nipple).

They will often present with bloody or clear nipple discharge, yet larger papillomas can also present initially as a mass.

They can appear similar to ductal carcinomas on imaging and therefore usually require biopsy. Some cases may be excised to ensure no atypical cells or neoplasia are present. Risk of breast cancer is only increased with multi-ductal papilloma and most are treated with microdochectomy.

Lipoma

A breast lipoma is a soft and mobile benign adipose tumour that are normally otherwise asymptomatic. They have low malignant potential and are usually only removed if they are significantly enlarging or causing symptomatic compressive or aesthetic issues.

Phyllodes Tumours

Phyllodes tumours* are rare fibroepithelial tumours. Phyllodes tumours are commonly larger, occur in an older age group, and are comprised of both epithelial and stromal tissue. They often grow rapidly.

They are difficult to clinically and microscopically differentiate from fibroadenomas, however around one third of Phyllodes tumours have malignant potential and 10% of benign tumours will recur after excision. Consequently, most Phyllodes tumours should be widely excised (or mastectomy if the lesion is large).

*The name derives from the Greek word ‘phyllodes’ meaning leaf, due to its characteristic leaf like projections of fibrous tissue seen on microscopy.

Adapted from work by KGH (A,C), Sarahkayb (B) and Nephron (D) [CC BY-SA 3.0], via Wikimedia Commons

Figure 1 – Histology of Benign Breast Disease (A) Fibroadenoma (B) Adenoma (C) Papilloma (D) Phyllodes

Clinical Features

As described above, benign breast lesions can present in a variety of ways.  However in general, benign breast lumps tend to be more mobile and have smoother borders than their malignant counterparts, which often have craggy surfaces, a firm consistency, and can be fixed to different layers of tissue. Malignant lesions tend to present as a single mass, whilst it is possible to get multiple benign breast lumps.

Differential Diagnosis

The mainstay of distinguishing between breast lumps is the Triple Assessment. The main differentials to consider include cysts, abscesses, and malignant lesions.

Investigations and Management

All suspicious breast lesions should undergo the triple assessment, warranting examination, imaging, and histology.

With benign breast lumps that have been confirmed, in most cases / subtypes reassurance and routine check up appointments are sufficient. However, if a breast lump cannot be confirmed to be benign or has malignant potential with atypical cells, they may be excised after a triple assessment.

For some women, benign breast lumps may cause symptoms, such as pain or discomfort, if they grow and therefore excision may also be the best option.