Most breast lumps are not breast cancer and non-cancerous lumps do not develop into breast cancer. The safest approach to all breast lumps is to have them examined by a medical professional because no matter how often you examine women’s breasts as a doctor or check your own breasts as a patient, it cannot be assumed that a lump in the breast is of no concern. We do not have eyes on our fingers which is why a clinical examination must be followed with a simple, non-threatening, non-painful investigation called an ultrasound or breast sonar (done by a radiologist, with a mammogram for women over the age of 35 years) The ultrasound can determine what the lump is.

The safest approach to all breast lumps is to have them examined by a medical professional.

If a doctor or patient is really concerned a triple assessment comprising of a clinical examination, sonar and/or a mammogram as well as a core needle biopsy will confirm what the lump is

Solid masses


These are highly mobile round, smooth, firm lumps usually found in a young woman’s breast (the teenager and the girl in her early twenties). It is sometimes called the breast mouse because it is so mobile and ‘runs’ from the examining hand.  These lumps do occur in older women though not commonly. Fibroadenomas come from the lobules (milk tissue) and are sensitive to female hormones like the other breast tissue from which they develop.

Most fibroadenomas get noticed around 1-2cm in size but they can grow to more than 5 cm. Women who have one, often find more when they start looking and it’s not uncommon to find lots, and in both breasts. A fibroadenoma can not become cancer, neither do they increase your risk of getting cancer. Once a doctor has confirmed your lump is a fibroadenoma using ultrasound and a core needle biopsy,  it can be left alone. Some may even disappear spontaneously. Remember that a clinical exam should be initially followed by an ultrasound.


If the fibroadenoma becomes painful, if it gets bigger than 3 cm (i.e. a giant fibroadenoma) or if you are worried about it, it can be removed with surgery via an incision around the nipple or base of the breast. Remember that surgery leaves both scars on the skin and in the breast tissue and can make breast investigations performed later in life more difficult to interpret.


If you already have a fibroadenoma and are pregnant, you can expect the size of the fibroadenoma to vary slightly during pregnancy and lactation, but this will not interfere with breastfeeding or milk production. Calcified fibroadenomas are sometimes found in elderly women as a hard, mobile lump that can be easily seen on a mammogram.

Cystosarcoma Phyllodes (Phyllodes Tumour)

Phyllodes tumours (PTs) take their name from the Greek word phyllon which means ‘leaf’ because of their leaf-shaped growth pattern. They can also behave like plants which are difficult to root out, like a weed in the garden. Unlike fibroadenomas, when they grow in the breast, they don’t form a neat shell around the outside, but instead they grow into normal breast tissue. That means when they are removed with surgery, if a rim of normal breast tissue is not taken out too, little bits can be left behind. Like the roots of a weed, they will cause the lump to grow back, often more aggressively than before.

Phyllodes do have a risk of a recurrence even if they are benign (non-cancerous),  they also have a risk of spreading or recurring if malignant (cancerous). The type of tumour and its risk to recur or spread (metastasise) can only be determined once it has been removed and examined microscopically. Once the grade of a Phyllodes tumour is established, you may need to undergo a second surgical procedure to ensure you have clear margins of disease free tissue of 1-2 cm, followed by reconstruction. Reconstructive options depend on factors such as breast size and patient choice, varying from breast reduction to other more extensive options.

Unlike ‘normal’ breast cancer there are no identified risk factors for having a Phyllodes tumour, nor does there seem to be a genetic predisposition. Unlike breast cancer which arises from the glandular elements of the breast, these are tumours that arise from connective tissue within the breast tissue. Malignant Phyllodes tumours don’t spread like breast cancers to lymph glands and usually just recur locally, however the more aggressive tumours can spread to the lungs and liver. Some can be so large (up to 30 cm in size) that complete removal of the breast and part of the chest wall is required

Because doctors don’t encounter Phyllodes tumours all that frequently, they are often misdiagnosed as benign fibroadenomas. Breast masses should never be brushed off as ‘harmless fibroadenomas’ and that is why most diagnoses today should only be undertaken by a specialist radiologist with the use of an ultrasound and guided core needle biopsy.

Any features on ultrasound that are not typical should result in a core needle biopsy, which involves a small biopsy done under local anesthetic. All masses, irrespective of diagnosis, should be followed up 3 or 6 months later by an ultrasound. Furthermore, any masses that grow, or are larger than 3 cm, should always be surgically removed.

Fat necrosis

Severe injury to the breast (e.g. from a motor vehicle accident) can cause fat necrosis. It can also occur after some breast reduction operations. The problem with fat necrosis is that it feels like a hard, irregular lump, which mimics breast cancer. The only way to tell the difference is through a mammogram and core needle biopsy. There is no treatment required for this problem and surgery is not advisable. Once the investigations have confirmed that the lump is fat necrosis, all that is needed is reassurance and monitoring it to see that it doesn’t get bigger or change its shape.

Breast hamartomas (Fibroadenolipoma)

This is not a common breast lump and can therefore go unnoticed or unrecognised by most doctors. Hamartomas of the breast are normally painless breast lumps which are softer and larger than fibroadenomas. These lumps have been likened to a ‘breast within the breast’ because they contain all the same types of tissue found in a breast. This may account for some diagnostic confusion especially if a Fine Needle Aspiration (FNA) is performed, because the cells that make up the breast tissue are difficult to differentiate from abnormal cells. It is usually possible to confirm diagnosis with a core biopsy rather than an FNA. On a mammogram, these lumps have a distinct picture showing a visible lump separated from the normal breast tissue by a thin white margin. They are often missed on ultrasound as they have the same density. If a clinical examination and core needle biopsy do not fully explain the lump, surgical removal is recommended.

Fibroadenosis (cyclical breast pain)

Breasts alter cyclically with the different stages of the menstrual cycle.  In the week prior to menstruation, the breast normally increases in size and sometimes becomes nodular, with pain. This can mimic a breast mass.

This is normally called ‘fibroadenosis’ but we think this term can be confusing and misleading sometimes because represents what is going on inside the breast at a tissue level but the process is normal. Breasts are uniquely different to palpation, some are smooth, some are nodular and the term should not be used as if this is abnormal or a disease of the breast.

All breasts have a certain amount of fibrosis (connective tissue) and adenosis (gland or milk tissue) and disease should be attributed to a woman with breast symptoms. If concerned, a breast ultrasound can aid the clinician in determining whether this is a mass or just nodularity.

Cystic masses

Breast Cysts

Breast cysts are masses that might look and feel like a lump but actually they are fluid-filled sacs within the breast. No one knows why they form but it can be due to the hormonal or structural changes in the breast that happen as you get older. Cysts occur in about 5% of pre-menopausal women in the years after childbirth and breastfeeding. They might be single or multiple, but often they are only picked up on mammogram or sonar. There are 3 types of cyst; simple cysts (clear); complicated cysts (with murky fluid) and complex cysts (which have a growth on the wall). Cysts  are easily diagnosed using an ultrasound and can be aspirated with a FNA. The fluid drawn from this type of cyst is usually yellow (simple cysts) or greenish (complicated) in colour. Simple cysts require no treatment; complicated cysts can become infected and may require antibiotics and needle drainage.

Provided there is no blood (red or black) in this fluid and that there is no residual lump remaining after the aspiration, no further treatment is necessary.  If there is blood or a residual lump, further evaluation is necessary.  This takes the form of sending the aspirate for cytology (it is a good principle to send all aspirates for cytology) and then to biopsy the residual mass if present under radiological guidance or to excise it surgically.

The most important information about pure breast cysts is that they do not cause cancer and they are no associated with cancer.


This is simply a cyst, found only in breastfeeding women that contains retained milk but has no signs of bacterial infection.  It can be treated by needle aspiration of the cyst and suppression of milk. Surgical excision can also be performed if necessary, though this is not a very common practice.