Look inside any human breast, even a male breast, and you’ll find around 15 to 20 lobes, collections of glandular tissue that radiate outward from the nipple “like the petals of a daisy,” according to the Mayo Clinic. Each lobe is itself divided into smaller groupings of tissue called lobules, which produce milk. Thin tubes, called ducts, connect each lobule to a small reservoir directly beneath the nipple.
How Does Breast Cancer Work?
Almost every breast cancer begins here, in the network of lobes and ducts that transport milk to the nipple:
- lobular carcinoma – a breast cancer that begins in the lobules
- ductal carcinoma – a breast cancer that begins in the milk ducts
Like every organ, breasts are made up of billions of cells. Cancer is what happens when these cells get out of control.
Normally, cells divide in a fairly orderly way. When an old cell dies, another cell will divide to replace it. Of course, in order to divide, a cell first has to copy its own genetic material, creating a duplicate that will act as the “blueprint” for a new cell. This replication process is rarely perfect; cells make all sorts of mistakes in copying their genetic material for a new generation. Most of these mistakes, or mutations, are perfectly benign. But sometimes, genetic mutations have a radical effect on the way cells behave and interact with their neighbors.
Metastasis Is The Hallmark Of Cancer
Cancer cells, for their part, are ones that have become immortal. Instead of dying off, they continue to divide uncontrollably, eventually creating a tumor. Some tumors aren’t cancerous, however.
Usually, cells are happy only in their own local environment. Stray too far from the community, and a number of chemical signals will instruct a cell to commit suicide. Cancerous cells have learned how to override these signals, allowing them to spread beyond the tissues in which they began. This ability to “metastasize,” and colonize distant regions of the body, is what we properly term “cancer.”
Where Does Breast Cancer Spread?
Breast cancers can spread far and wide, although most tumors metastasize first to the system of lymph nodes directly surrounding the breast. Cancers can also spread more locally, invading the muscle and fat tissues of the breast itself. Once cancerous cells have reached the bloodstream, they can ultimately reach any organ that requires a blood supply, although the brain, liver and lungs are particularly common sites of metastasis for breast cancer. The disease also invades bone tissue with regularity, especially the ribs, spine and pelvis.
Most breast cancers, though, are diagnosed before metastasis. That’s rare in the world of cancer, and surprisingly hopeful. In fact, nearly 90% of the women diagnosed with breast cancer between 2006 and 2012 survived for at least five years after receiving their diagnosis. Of those women:
- 61% were diagnosed before their cancers had spread beyond the site of origin
- 31% were diagnosed after their cancers had spread to nearby lymph nodes
- 6% were diagnosed after their cancers had spread further to other organs
Routine screenings, including mammograms, have likely contributed to these numbers, since some women with early breast cancers don’t experience any symptoms. Mammograms, for that matter, probably aren’t as beneficial as we would hope. While this fact is rarely publicized, decades of research suggest that extreme vigilance may actually hold more risks than benefits.
Are There Early Breast Cancer Symptoms?
Yes, although around 10% of women who are eventually diagnosed with breast cancer never experience symptoms at all.
While they’re probably the most commonly-referenced sign of breast cancer, lumps aren’t always malignant. In fact, up to 85% of all breast lumps are benign, although our increased reliance on mammography has led to a jump in the number of benign lesions erroneously diagnosed as cancer. Doctors also seem to overreact to abnormalities, pushing patients into aggressive treatments for tumors that would probably turn out harmless. Mother Jones says women are three times more likely to receive unnecessary treatment after an abnormal mammogram than they are to undergo life-saving therapies.
Today, breast self-exams appear to be just as effective as advanced diagnostic techniques, including MRI, according to Medscape Medical News. In general, every self-exam should be focused on recent changes in the appearance or feeling of a breast. Any abnormal change in a breast should be looked at by a doctor, from unexplained shrinkage to a suddenly inverted nipple. Particular attention should be paid to changes that affect only one breast, since it’s highly unlikely that cancer would develop simultaneously in both breasts.
Education is crucial to early detection. We have a fair understanding of what factors put people at a higher risk of developing breast cancer:
- being overweight
- taking menopausal hormone therapies
- using oral contraceptives
- drinking alcohol
- not having children, or having a child after the age of 35
Women who are considered “high-risk,” as well as younger women who usually don’t receive routine screening tests, have “a critical need for self-exam,” says Barbara Smith, an associate professor of surgery at Harvard Medical School.
In asymptomatic cases, mammograms may miss up to 20% of cancers.
Do We Know What Causes Breast Cancer?
Not really, and researchers still aren’t sure how those risk factors contribute to the development of cancerous breast cells. Genetic research, however, has opened the door to a new world of understanding.
Proto-oncogenes, for example, are bits of genetic information that help cells divide. But when one of these genes mutates, or gets over-copied, it can remain active longer than it should, or initiate divisions continually. Her2 is one such oncogene, which has been found to exacerbate the progression of some aggressive breast cancers.
Tumor suppressor genes have a roughly opposite effect on cells. Some of these genes instruct cells to commit suicide, while others repair cellular damage. Obviously, damaging one of these genes can lead to uncontrollable cellular growth, and thus cancer. Two tumor suppressors in particular have received a lot of attention recently: BRCA1 and BRCA2. Women can inherit mutated versions of these genes from their parents. We now have genetic tests that can identify women who carry the mutations, informing better treatment decisions, including preemptive mastectomies.
Can You Inherit Cancer?
No, but as we’ve seen, you can inherit genetic mutations that greatly increase your risk of developing breast cancer. Breast cancer itself, though, isn’t solely a genetic condition. In fact, only between 5% and 10% of cases are directly caused by malfunctioning BRCA1 or BRCA2 genes. Genetic mutations may put a thumb on the scale, but they rarely lead to cancer on their own.
With that being said, a faulty BRCA1 or BRCA2 gene seems to put a very heavy thumb on that scale. While around 12% of women from the general population will develop breast cancer, between 55% and 65% of women who inherit a defective BRCA1 mutation will get cancer by the age of 70. Even so, most cases are a result, not of genetic factors in isolation, but genetic factors in tandem with lifestyle and environmental influences.