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Breast "self-awareness," and the relationship between breast cancer and fertility

Breast "self-awareness," and the relationship between breast cancer and fertility

7 min read

It’s October, and besides the re-emergence of pumpkin spice lattes, that means it’s Breast Cancer Awareness Month.

We know you’ve heard it before, but we’ll say it again: Breast cancer impacts approximately 1 in 8 women in their lifetimes, so being proactive about your breast health is extremely important. Some risk factors that increase the chances of breast cancer (like aging and menopause) are beyond our control, but others, like smoking, are modifiable.

Breast Cancer Awareness Month brings us the opportunity to educate ourselves, increase our awareness, and improve our ability to make informed decisions for our fertility and health.

Everything you need to know to stay on top of breast health

When thinking about your breast health, most medical groups recommend breast self-awareness over breast self-examination.

The American College of Obstetricians and Gynecologists (ACOG) and the American Cancer Society agree that routine self-breast exams aren’t actually recommended for average-risk women due to the increased prevalence of false positives leading to unnecessary screening.

Instead, breast “self-awareness” is recommended. This involves actively looking out for any changes in your breasts’ and surrounding skins’ appearance, texture, and sensitivity. In increasing your breast self-awareness, you’ll be more in tune with anything that appears abnormal and more likely to detect and treat any issues early on.

An important starting point is knowing the anatomy of the breasts — and knowing that the breasts are hormonally responsive tissues. Fluctuations in hormones at different times of the menstrual cycle, pregnancy, lactation, and menopause can change the look and feel of the breasts.

We’ll cover the changes you can expect in your breasts later on, but let’s start with everything you need to know about the anatomy of your breasts.

Breast anatomy, from the outside in

The outsides of the breasts include the following components:

  • The nipple is the raised region on the darker surface of the breast (the areola) where milk leaves the breast during lactation.
  • The areola has both hair follicles and sebaceous glands, which lubricate the skin if someone chooses to breastfeed.
External and internal breast anatomy.

The insides of the breasts are made up of a combination of connective tissue, glandular tissue, and fatty tissue:

  • The connective tissue contains ligaments and holds the breast tissue in place.
  • The glandular tissue is composed of the breast lobes and breast ducts. The 15-20 lobes each contain lobules (think little sacs that look like a cluster of grapes) that produce milk, and the ducts are thin tubes that carry milk from the lobules to the nipple.
  • The fatty tissue makes up the rest of the breasts and largely determines their size.

In our younger years, breasts tend to have a higher composition of connective and glandular tissue, making the breasts appear more “dense” on mammograms — meaning the tissue looks whiter. As we age, this dense tissue is replaced by increased fatty tissue, which is less dense and appears black on mammograms.

Breast changes you can expect throughout your lifetime

There are several times throughout your lifetime when breast changes may be notable:

  1. Changes throughout the menstrual cycle: Immediately before and possibly during menstruation, you may notice breasts that feel swollen, firm, or even tender to the touch due to excess fluid accumulation. These breast changes are secondary to the hormone progesterone, which rises after ovulation and stays elevated in preparation for a fertilized egg to implant in the uterus. If you don’t get pregnant, the levels of progesterone fall, and you get your period. The breasts’ response to progesterone may be one sign of PMS that clues you in to the fact that you’re about to get to your period.
  2. Changes as you get older: When you’re younger, you’re more likely to have dense breasts, meaning your breasts have more glandular and connective tissue compared to post-menopausal people who tend to have fattier breast tissue. Dense breasts can make it more difficult to assess possible breast masses because the breast tissue may obscure them.
  3. Changes during pregnancy: Pregnancy is a naturally high hormonal state and these hormones can impact the feel of your breasts. Due to elevated estrogen and progesterone levels in pregnancy, you may notice significant breast changes including enlargement, darkening of the areolas, increased lumps due to an increase in milk glands, and decreased breast density.

Breast symptoms to pay attention to

Approximately 90% of breast masses in women in their 20s to early 50s are non-cancerous. If you notice a breast lump, the most important first step is excluding breast cancer. Report any new and concerning lumps or worrisome breast changes to your healthcare provider, no matter what age you are. Early detection and early treatment is key in reducing breast cancer mortality.

Beyond breast lumps, here are a few other changes to be on the lookout for when checking in with your breasts:

Any time you notice a new breast lump or concerning breast changes, it’s important to reach out to your healthcare provider to help you investigate what might be going on.

Breast cancer and fertility

Being diagnosed with breast cancer at any age is scary, overwhelming, and stressful. But for people who want to have children and haven’t started or completed childbearing, it can add another layer of anxiety. The chemotherapeutic drugs that are used to treat breast cancer can be damaging to the ovaries, resulting in diminished ovarian reserve (accelerated reduction of egg count), ovarian failure (loss of function in the ovaries), and amenorrhea (no periods).

If you’re diagnosed with breast cancer in your childbearing years and still want to have children, it’s important to consider meeting with a fertility specialist to discuss your options of fertility preservation (like egg freezing) prior to starting chemotherapy. Studies on fertility preservation in breast cancer patients show no increase in disease recurrence or decrease in survival.

Risk factors for breast cancer

There are a few situations and conditions that are shown to increase the risk of breast cancer:

  • Being a woman (who was assigned “female” at birth)
  • Increasing age
  • Early start of periods
  • Late menopause
  • Not giving birth (nulliparity)
  • Not breastfeeding
  • Smoking
  • Having dense breasts on mammograms
  • Prior exposure to high-dose chest irradiation in young women
  • Genetic mutations like BRCA 1 and BRCA 2

There are also a few populations with higher rates of breast cancer. Black women under age 40 have a higher incidence of breast cancer than white women under age 40. Additionally, the baseline risk of having a BRCA mutation is approximately 1 in 400 people with ovaries — but some ethnicities, such as Ashkenazi Jewish people, have significantly higher risk of having a BRCA mutation at 1 in 40.

Why is being a woman (who was assigned “female” at birth) considered a risk factor?

While men are at risk of developing breast cancer (approximately 3,000 cases annually), the risk is significantly higher in women with a rate of approximately 270,000 new cases each year. As compared to men’s breast tissue, women’s breast tissue is more metabolically active (changing and growing) due to the effects of estrogen and progesterone on the breast tissue.

Why is not giving birth (nulliparity) considered a risk factor?

Nulliparous women (never having been pregnant) have a 20-40% higher rate of breast cancer compared to a woman who has given birth before age 25. One explanation may be that the hormones from pregnancy protect the breast tissue against DNA damage in the future. Additionally, women who are older at the time of their first birth also have a slightly higher risk of breast cancer compared to women who were younger at first birth. The mechanism behind this is that full breast cell differentiation and maturation occur during and after pregnancy — the later you have a pregnancy, the later you’re exposing those cells to changes.

The relationship between breast cancer, birth control, and fertility treatments

A common question I get as an OB-GYN is this: “Will the hormones I take in birth control or during fertility treatments will increase chances of breast cancer in the future?”

Birth control pills have little to no association with an increased risk of breast cancer according to several large randomized controlled trials. A 2017 study from the New England Journal of Medicine noted a very slight increase in the risk of breast cancer with oral contraceptive use, however, the study is limited by its observational nature and inability to control for other factors that may increase the risk of breast cancer.

When it comes to fertility treatments, the short answer is no — long-term studies do not appear to show an increased risk of cancer. The longer answer is that both nulliparity (never having been pregnant) as well as older age at first birth both slightly increase the risk for breast cancer, and both are more common in people with infertility.

Additionally, women over 40 pursuing infertility treatment may be more likely to undergo baseline mammograms prior to starting in-vitro fertilization (IVF), so the rate of earlier detection may be higher. As opposed to fertility drugs leading to a higher risk of breast cancer, the more likely answer is that underlying infertility in women may contribute to the slightly higher risk seen in some studies.

It’s worth noting that one study found an association between infertility diagnosis, the use of fertility treatment, and a higher absolute breast density on mammograms. The significance of this study is that women with extremely dense breasts have an approximate four-fold higher risk of breast cancer. But it’s important to acknowledge several weaknesses of this study: there is no information on the duration of infertility, there is no information on the specific treatment or cause of infertility (male factor, tubal factor, endometriosis, etc.), and due to the design and methodology of this study, there’s a high risk of recall bias — an inaccurate recollection of memories and experiences from the study participants’ pasts.

Ultimately, the best way to increase your awareness of breast cancer and health is to stay attuned to any changes, learn your family history, and find out if there are any potential risk factors that may increase your risk for breast cancer. The more informed we are about what is normal and what is not, the more proactive we can be regarding our breast health.

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Dr. Temeka Zore

Dr. Temeka Zore, MD, FACOG is a fellowship-trained reproductive endocrinologist and infertility specialist and board-certified OB-GYN at Spring Fertility in San Francisco.

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