What is breast cancer ?
Breast cancer is a
cancer that forms in the tissues of the breast – usually in the ducts (tubes
that carry milk to thenipple) or lobules (glands
that make milk). It occurs in both men and women, although malebreast cancer is
rare.
Different types of breast cancer
Breast cancer can be
categorised by whether it is non-invasive or invasive:
Non-invasive breast cancer (in situ)
Ductal carcinoma in situ
(DCIS) is a pre-malignant lesion – it is not yet cancer, but can progress to
become an invasive form of breast cancer. In this type of cancer,
the cancer cells are in the ducts of the breast but have
not spread into the healthy breast tissue.
Lobular neoplasia
(previously called lobular carcinoma in situ) is when there are changes
in the cells lining the lobules, which indicate that
there is an increased risk of developing breast cancer in the future. Lobular neoplasia is not actually breast cancer, and although women with
lobular neoplasia will have regular check-ups,most will not develop breast
cancer.
Invasive breast cancer
Invasive breast cancer is the name given to a cancer that
has spread outside the ducts (invasive ductal
breast cancer) or lobules (invasive lobular breast cancer). These can be further classified by their
histology; for example, tubular, mucinous, medullary and
papillary breast tumours are rarer subtypes of breast cancer.
Breast cancer is also
categorised by how advanced the disease is:
Early breast cancer
Breast cancer is
described as early if the tumour has not spread beyond the breast or axillary lymph nodes (also known as Stage 0 IIA breast cancer). These cancers are
usually operable and the primary treatment is often surgery to remove the
cancer, although many patients also have preoperative neoadjuvant systemic therapy.
Locally-advanced breast cancer
Breast cancer is
locally-advanced if it has spread from the breast to nearby tissue or lymph nodes (Stage IIB III). In the vast majority of
patients, treatment for locally-advanced breast cancer starts with systemic therapies. Depending on how far the cancer has spread,
locally-advanced tumours may be either operable or inoperable (in which
case surgery may still be performed if the tumour shrinks
after systemic treatment).
Metastatic breast cancer
Breast cancer is
described as metastatic when it has spread to other parts of the body, such as
the bones, liver or lungs (also called Stage IV). Tumours at distant sites are called metastases. Metastatic breast
cancer is not curable but is treatable.
Advanced breast cancer
Advanced breast cancer
is a term used to describe both locally-advanced inoperable breast cancer and metastatic
breast cancer.
Subtypes based on hormone receptor status and HER2 gene expression
• The growth of some tumours is stimulated by the hormones oestrogen and progesterone. It is important to find out whether a tumour is oestrogen
receptor (ER) or progesterone
receptor (PgR) positive or
negative, as tumours with a high level of hormone receptors can be
treated with drugs that reduce the supply of hormone to the tumour.HER2 is also a receptor that is involved in the
growth of cells and is present in about 20% of breast cancers.
Tumours that have a high level of HER2 can be treated with anti-HER2 drugs.
Tumours that don’t have ER, PgR or high levels of HER2 are described as triple-negative tumours.Tumours can be classified into subtypes based on
hormonal and HER2 receptor status as follows:luminal A-like (ER and PgR positive, HER2 negative tumours), luminal B-like (ER and/or PgR positive, HER2 positive
or negative tumours), HER2 overexpressing (ER and PgR negative, HER2 positive tumours) and basal-like
(triple-negative tumours).
What are the symptoms of breast cancer
Symptoms of breast cancer include:
• A lump in the breast
• Change in the size or shape of the breast
• Dimpling of the skin or thickening in the breast
tissue
• An inverted nipple
• Rash on the nipple
• Discharge from the nipple
• Swelling or a lump in the armpit
• Pain or discomfort in the breast that doesn’t go
away
• Skin redness
• Skin thickening
You should see your doctor if you experience any of these symptoms. However, it
is important to remember that these symptoms may also be caused by other
conditions. Certain symptoms may indicate the presence of metastases – for
example, a lump or swelling under the armpit, in the breast bone or collar bone
area may be a symptom of lymph node metastases. Pain in a bone or a bone
prone to fracture might suggest bone metastases, and lung metastases may
cause symptoms of ongoing chest infections, persistent cough and
breathlessness. It’s important not to be alarmed by
these symptoms as they don’t necessarily mean that you have metastases;
however, you should discuss any concerns with your doctor.
Common breast cancer
Breast cancer is a leading cause of
cancer-related deaths in women, with almost 1.7 million cases diagnosed per year and more than half a million deaths every year (Ferlay et al. 2013). In developed countries, 1 in every 8 women will develop breast cancer in their lifetime. In Europe, there is
a breast cancer diagnosis every 2 minutes and a death due to breast
cancer every 6 minutes. Breast cancer mostly affects older women, with the
majority of patients being over the age of 50 when
diagnosed, although around 1 in 5 breast cancers are diagnosed before the age of 50. Breast cancer in men is rare and makes up around 1%
of breast cancer cases. Female breast cancer incidence rates vary widely
between regions, with the highest incidence rates in Western Europe and the United States, and the lowest in Africa and Asia.
Higher breast cancer incidence in more developed countries
reflects the presence of more breast cancer risk factors in these
countries (Torre et al. 2016). However, the incidence
of breast cancer in developing countries is rapidly increasing. Despite higher
incidence rates, deaths due to breast cancer in most
Western countries have decreased in recent years due to improved treatment and earlier detection, but have substantially increased
in developing countries. In developed countries, around 10–15% of
patients have advanced disease at diagnosis, compared with 40–90% in developing
countries
(Balogun and Formenti 2015)
Causes of breast cancer
The precise cause of
breast cancer is unknown, but several risk factors for developing the disease
have been identified. It is important to remember that
having a risk factor increases the risk of cancer developing but it does not mean that you will definitely get cancer. Likewise, not having
a risk factor does not mean that you definitely won’t get cancer.
Most important risk factors
• Female gender
• Exposure to ionising radiation
• Increasing age
• Having fewer children
• Genetic predisposition (family history
or mutations in certain genes)
• History of atypical hyperplasia
• Obesity
• Exposure to oestrogens
• Alcohol
Family history plays a
very important role in whether
or not a woman will
develop breast cancer. Women
with a first-degree
relative (parent, sibling or child) with breast cancer have
twice the risk of developing
breast cancer compared
with a woman with no such family history. The risk is increased 3-fold if
that relative was diagnosed with breast cancer before the menopause.