38 Breast cancer
Breast cancer is the commonest cancer affecting women: 1 in 10 women develop the disease in the UK. All women aged 50 to 70 years in the UK are currently invited for mammography. Less than 1% of breast cancers occur in males, where prognosis is worse because they present later.
Aetiology
genetics: 5% of cancers are caused by breast cancer genes (BRCA1 and BRCA2); they give an 80–90% risk of developing cancer
Clinical features
Breast cancer can present with specific features (Fig. 3.38.1), during screening (mammography; Fig. 3.38.2), which has reduced mortality by 30%, or as metastatic disease (back pain (vertebrae), breathlessness (lungs), jaundice/abdominal distension (liver)).
Pathology
Ductal carcinoma is the most common type. The rarer variants (lobular, tubular, cribriform, mucinous, medullary) have distinctive histological appearances and a better prognosis.
Oestrogen receptor (ER) expression
A tumour expressing ERs is dependent on oestrogen and susceptible to hormone therapies. The ER status is determined histologically; ER-positive tumours (more common) have a better prognosis.
Ductal carcinoma in situ
This is a non-invasive cancer where malignant cells have not penetrated the epithelial basement membrane and so have not yet extended out of the breast duct system. It may be detectable by mammography and biopsy of microcalcification before invasion occurs and is usually asymptomatic.
Paget’s disease of the nipple
This is a skin manifestation (patch of eczema around the nipple) of an underlying breast malignancy (1% of cancers). Ductal carcinoma in situ is often associated early on, but it will develop into invasive cancer if untreated. An underlying lump may be palpable (not always), and mammography and nipple biopsy should be performed.
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