Skip to Main Content


Neither the cause of breast cancer, one of the most feared and emotion-engendering diseases, nor the means of preventing it are absolutely known.


Breast lumps are common and their discovery by a woman provokes considerable anxiety and emotion (which is often masked during presentation) because, to many, a breast lump means cancer. Many of the lumps are actually areas of thickening of normal breast tissue. Many other lumps are due to fibrocystic disease with either fibrosis or cyst formation or a combination of the two producing a dominant (discrete) lump. However, a good working rule is to consider any lump in the breast as cancer until proved otherwise. See TABLE 101.1 for causes of breast lumps in a specific outpatient study.

Table 101.1Causes of breast lumps in women: diagnostic strategy model

The genetic predisposition to breast cancer continues to be delineated with the strong predisposition from mutations in the genes BRCA1 and BRCA2. Refer to CHAPTER 18.

Key facts and checkpoints

  • The commonest lumps are those associated with mammary dysplasia (32%).1 See TABLE 101.1.

  • Fibrocystic disease is also a common cause of cysts, especially in the premenopause phase.

  • Over 75% of isolated breast lumps prove to be benign, but clinical identification of a malignant tumour can only definitely be made following aspiration biopsy or histological examination of the tumour.1

  • The investigation of a new breast lump requires a very careful history and the triple test.

  • Breast cancer is the most common cancer in females. The risk of developing breast cancer before age 85 in Australian women is 1 in 8.2

  • Breast cancer is uncommon under the age of 30 but it then steadily increases to a maximum at the age of about 60 years, being the most common cancer in women over 50 years. The average age of diagnosis is 60.7 years.3 FIGURE 101.1 highlights the changing frequencies of different discrete breast lumps with age.4

  • About 25% of all new cancers in women are breast neoplasms.

  • A ‘dominant’ breast lump in an older woman should be regarded as malignant.

FIGURE 101.1

Changing frequencies of different discrete breast lumps with age

Source: From Dixon & Mansel.4 Courtesy of Anthea ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.