Breast cancer is one of the leading causes of death among women, responsible for 685,000 deaths in 2020 alone, according to the World Health Organization (WHO). It is also the second-most diagnosed cancer among women with 2.3 million cases in 2020.
But not all breast cancers are the same — the type is determined by factors such as which cells have become cancerous, the presence or absence of certain receptors and the extent to which the cancer has spread.
It is important to be aware of the different types of breast cancer so one is more likely to notice the condition in its early stages when treatment is easier and more successful.
One way of grouping breast cancers is based on whether they are still in their original spot or have spread to other areas. Cancers which haven’t spread beyond their place of origin are called ‘in situ’ — meaning ‘in the original place’. These are in the earliest stages. Cancers which have spread to nearby regions or other parts of the body are called ‘invasive’. These are in the later stages.
Another way of grouping breast cancers is based on their point of origin. If the breast cancer starts in cells in the milk ducts, it is called ‘ductal’. If it starts in the lobules (the glands that produce milk), it is called ‘lobular’. ‘Carcinoma’ refers to a cancer that starts in the epithelial cells that line tissues and organs throughout the body.
Common types of breast cancer among women
The four main types of breast cancer are as follows:
Ductal carcinoma in situ
Ductal carcinoma in situ (DCIS) is a type of breast cancer in which cells in the lining of the breast milk duct become cancerous. It is a non-invasive cancer, meaning the cancer hasn’t spread outside of the ducts. As this type of cancer is in the early stages, it is highly treatable. But if left untreated, it can spread to the surrounding breast tissue.
Invasive ductal carcinoma
Invasive ductal carcinoma (IDC) is a type of invasive breast cancer in which cancerous cells that started in the lining of the milk ducts have spread to surrounding breast tissue or other parts of the body. IDC is the most common type of breast cancer, accounting for 70-80 per cent of all breast-cancer diagnoses, according to the Texas-based National Breast Cancer Foundation. It is also the most common type to affect men.
Lobular carcinoma in situ
In a case of lobular carcinoma in situ (LCIS), cells in the lobules or milk-producing glands become cancerous. It is also a non-invasive cancer, meaning it hasn’t spread to surrounding breast tissue or other parts of the body. LCIS is highly treatable and rarely becomes invasive. However, having LCIS in one breast increases the chances of developing cancer in the other breast.
Invasive lobular carcinoma
Invasive lobular carcinoma (ILC) is a type of breast cancer in which the cancerous cells that started in the lobules have spread to surrounding tissue or to other parts of the body. It is the second-most common type of breast cancer. Unlike other types, ILC is less likely to be detected by mammograms and an MRI is usually needed to detect it.
Special types of breast cancer among women
There are other types too, with special characteristics:
Triple negative breast cancer
Triple negative breast cancer is one in which the three most common types of receptors known to fuel breast cancer growth are absent. These are estrogen receptors, progesterone receptors and hormone epidermal growth factor receptor 2 (HER-2).
Common treatments like hormonal therapy and drugs that work by targeting estrogen, progesterone and HER-2 gene cannot be used to treat this condition. Instead, chemotherapy is used and is, in fact, more effective in treating triple negative breast cancer in the early stages than many other types of cancer.
This type of cancer can also be more aggressive and more difficult to treat, with higher chances of it spreading and recurring.
Inflammatory breast cancer
Inflammatory breast cancer (IBC) is a type of aggressive and fast-growing breast cancer in which cancer cells have entered the skin and lymph vessels of the breast. Symptoms begin to appear when the lymph vessels become blocked by cancer cells.
No distinct lump can be felt but the breast becomes red, swollen and warm, with the skin becoming pitted like an orange peel due to dilation of pores. Small rashes may also appear accompanied by persistent itching. The nipple may inverse, flatten or dimple.
IBC is usually diagnosed after a biopsy. It requires aggressive treatment and is the only type of breast cancer to require urgent treatment starting with chemotherapy.
Metastatic breast cancer
When breast cancer has spread to other parts of the body — like the lungs, liver, bones or brain — it is called metastatic breast cancer. It is classified as Stage-4 breast cancer.
The symptoms vary, based on which tissues or organs have been infected.
Metastatis in the bone may cause severe, progressive pain, swelling and weak, fragile bones. Metastatis to the brain may cause persistent headaches, vision disturbances, seizures, nausea or vomiting and personality changes. Metastatis in the liver may cause jaundice, itching, rashes, abdominal pain, appetite loss, nausea and vomiting. Metastatis to the lungs may cause chronic cough, trouble breathing, chest pain, fatigue, weight loss and poor appetite. If you notice any of these symptoms, you should report them to your physician.
Rarer types of breast cancer among women
There are some types that are less commonly seen:
Medullary carcinoma is a rare subgroup of breast carcinomas. Only 3-5 per cent of breast cancer cases are of this type. It can usually be detected by a mammogram but can often feel like a spongy mass rather than a lump. Medullary carcinoma usually carries a more favourable prognosis as compared to ductal carcinomas.
Tubular carcinoma gets its name from the fact that when cancer cells of this type of cancer are observed under a microscope, they appear to have a tubular structure. Only 2 per cent of breast cancer diagnoses are tubular carcinomas. Like medullary carcinoma, it can usually be detected by a mammogram and the affected area feels spongy rather than lumpy. It is most commonly found in women over 50 years of age and responds well to hormonal therapy.
Mucinous carcinoma is a type of breast cancer which causes mucus production. It also results in cancer cells having poorly defined shapes. Only 1-2 per cent of breast cancer cases are mucinous carcinomas. Most have a favourable prognosis.
Mammary Paget disease
Mammary Paget disease, also known as Paget disease of the breast and nipple, is a rare type of cancer that affects the skin of the nipple and areola. In most cases, when Paget disease is evident on the nipple or areola, there are one or more tumors present inside the same breast, generally ductal carcinoma. The prognosis depends on a variety of factors, including whether the cancer is invasive or not and if it has spread to lymph nodes. Only 1-3 per cent of breast cancer diagnoses are mammary Paget disease.