Original of this article was published on ZRT Laboratory Blog. Last reviewed: May 2026.
Having breasts, or just being a woman, is indeed the biggest risk factor for breast cancer, since the disease is 100 times more common in women than in men. But given the controversies that continue to rage about the benefits of screening — for example, a mammogram may not pick up the most invasive and deadly types of breast cancer — it seems appropriate to step back and look at what breast cancer really is, what it is not, and who is at the most risk.
What Breast Cancer Is Not
Breast cancer is not the leading cause of death in women, or even the leading cause of cancer death. The most prevalent cause of death in women, responsible for 1 out of every 4 deaths, is heart disease. While all types of cancer come a close second to heart disease as a cause of death, in both men and women the leading cause of cancer death is lung cancer, accounting for 25% of those cancer deaths. Breast cancer is the second leading cause of cancer death in women, accounting for 15% of all cancer deaths.
It is also important to understand that breast cancer is not just one disease. There are many types, with different attributes and degrees of invasiveness. When a breast tumour is confined to the breast, it doesn’t kill you. Cancer only becomes deadly when it invades other tissues and organs, in a process called metastasis. One common type, ductal carcinoma in situ (DCIS), accounts for 1 in 5 new breast cancer diagnoses; it is not invasive, is easily picked up on a routine mammogram, and can be completely cured.
What Breast Cancer Is
The most common types of breast cancer and their key attributes:
1. Invasive ductal carcinoma (IDC) — The most common type, accounting for 80% of invasive breast tumours. It originates in the milk ducts, invades through the duct wall, and grows into the fatty breast tissue. It can be detected early via mammogram but if left untreated can metastasise via the lymphatic system and bloodstream.
2. Ductal carcinoma in situ (DCIS) — Cancer cells lining the milk ducts that remain “in situ” and have not spread through the duct walls. Completely cured by treatment, but may develop into invasive cancer if left untreated. Accounts for 20% of new breast cancer diagnoses.
3. Lobular carcinoma in situ (LCIS) — Cancer cells form in the lobules of the milk-producing glands but do not invade the lobule walls. Does not become invasive if left untreated, but women with LCIS are at a 7–11 fold increased risk of developing invasive breast cancer and should have regular checkups and mammograms.
4. Invasive lobular carcinoma (ILC) — Begins in the lobules and can metastasise to other parts of the body. Harder to detect via mammogram than IDC, but rarer, accounting for only 10% of invasive breast cancers.
5. Inflammatory breast cancer — Accounts for only 1–3% of all breast cancers but has a greater chance of spreading than IDC or ILC. Often mistaken for a breast infection and does not show up on a mammogram as there is no lump. Instead, cancer cells block lymph vessels in the skin, which looks red, feels warm, and can have a pitted appearance like orange peel.
6. Paget’s disease of the nipple — Almost always associated with either DCIS or IDC. Begins in the milk ducts and spreads to the nipple and areola, which appear crusted, scaly and red. Accounts for only 1% of all breast cancer cases.
Triple-Negative Breast Cancer
Breast cancers are also classified according to hormone receptor status. About 75% of breast cancers are oestrogen receptor (ER) positive and proliferate in response to oestrogen; about 65% of ER positive tumours are also progesterone receptor (PR) positive. Hormone receptor positive breast cancers grow much more slowly and are more likely to respond to hormone therapy with agents such as tamoxifen or aromatase inhibitors.
The role of progesterone and its receptors in breast cancer is complex and controversial. The addition of synthetic progestins to postmenopausal oestrogen therapy has been consistently linked with increased risk of breast cancer, while oestrogen alone or with natural progesterone has not. Understanding your own oestrogen and progesterone balance is therefore clinically meaningful. Our Comprehensive Female Saliva Hormone Profile (LCMS) measures oestradiol, progesterone, testosterone, DHEA-S and cortisol from a simple at-home saliva sample — giving you and your practitioner a clear picture of your oestrogen/progesterone ratio.
About 20% of breast cancers make excess amounts of the growth-promoting protein HER2/neu. These cancers grow and spread more aggressively but are likely to respond to drugs that specifically target the HER2 protein, such as Herceptin and Tykerb.
Triple-negative breast cancers lack hormone receptors and the HER2 protein, meaning they do not respond to hormone therapy or HER2-targeting drugs. In these cases, chemotherapy is used for treatment even in early stages of the disease.
Who Is at Risk of Breast Cancer?
As women get older, their risk of developing breast cancer increases, as does the likelihood that the type of breast cancer is invasive. Some susceptibility is conferred by mutations in genes inherited from a parent, particularly in the BRCA1 and BRCA2 genes; heredity is thought to represent about 5–10% of breast cancer cases.
Other risk factors include:
- Higher lifetime exposure to endogenous oestrogens, due to earlier onset of menstruation and/or later onset of menopause
- Being overweight or obese
- Drinking alcohol
- Heavy smoking
- Shift work, leading to reduced melatonin production (melatonin is protective against cancer)
For women who want a comprehensive view of the hormonal and neurochemical factors that may influence breast cancer risk, our Women All-In-One Test – Hormones, Neurotransmitters & Heavy Metals covers sex hormones, adrenal markers, neurotransmitters and toxic elements — with specialist interpretation included.
What Can We Do About It?
While some risk factors are unavoidable, such as gender and age, much can be done through education, screening, and lifestyle adjustment to put women in control of their own risk and help avoid the more serious consequences of breast cancer. For women concerned about the interaction between shift work, melatonin disruption and hormone balance, our Neurotransmitter & Saliva Hormone Test I combines a full saliva sex hormone panel with a dried urine neurotransmitter profile — measuring serotonin, dopamine, GABA and key hormones in a single at-home test.
Original of this article was published on ZRT Laboratory Blog.