How Does Breast Size Affect Breast Cancer?

Separating Medical Fact From Urban Myth

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There is no scientific evidence that links breast size with breast cancer. Obesity puts women at a higher risk of breast cancer, and women who are overweight often have larger breasts. So, this could be one reason that contributes to the association.

People may also assume that finding a lump in their breast would be harder if you wear a triple-D cup compared to someone who wears, say, an A cup.

This article reviews the risk factors of breast cancer including gender, age, weight, family history, genetics, alcohol consumption, and dense breast tissue.

Nurse evaluating mammogram results
andresr / Getty Images

Breast Size and Breast Cancer Risk

There have been no large, peer-reviewed studies that support breast size as a factor in the development of breast cancer.

Obesity plays a significant role in the development of breast cancer, especially for post-menopausal women. Often, obese women have larger breasts than the average woman, which may suggest that those with larger breasts are at higher risk. However, it is more likely that weight or body mass index (BMI) is the risk factor rather than actual breast size.

Factors in Assessing Breast Cancer Risk

Beyond weight, there are key factors you should consider when assessing your breast cancer risk. Gender, age, family history, genetic predisposition, and alcohol consumption are a few known risk factors.

Gender and Age

Being a woman and growing older are the greatest risk factors for breast cancer. While it can occur at a younger age, most breast cancer is found in women 50 years and older.

Family History of Breast Cancer

Up to 10% of breast cancer cases are associated with family history. Research shows that having a first-degree relative (parent, sibling, or child) with breast cancer doubles your risk.

The risk increases more if your family member was young or male. There is also an increase in risk if second-degree relatives (aunts, uncles, nieces, nephews, grandparents, or grandchildren) from either side of your family have had breast cancer.

Familial Patterns That Increase Breast Cancer Risks

Some of the familial patterns that increase risk include:

  • Family members with multiple types of cancer
  • First or second-degree family member with high-grade prostate cancer
  • Multiple first or second-degree relatives with breast cancer
  • Male family member with breast cancer
  • More than one family member with the same type of cancer
  • Family member with cancer in both breasts or ovaries
  • Relative with both breast cancer and ovarian cancer

If you have any of these familial risk factors, talk to your healthcare provider. They may suggest more intensive breast screening (such as at an earlier age) or genetic testing.

Alcohol Consumption

Research shows that women who drink a moderate amount of alcohol increase their breast cancer risk by approximately 10%. Because alcohol can increase estrogen levels, this is especially true for estrogen receptor (ER) positive breast cancer.

Heavy alcohol use can also directly damage deoxyribonucleic acid (DNA) in the cells of breast tissue. Damage like this can cause cells to multiply abnormally and at a heightened rate, giving rise to precancerous and cancerous tumors.

Genetic Predisposition

When a mutated gene has been passed down from a parent, including the father, it increases a woman's chance of breast cancer. The most common genetic mutations associated with breast and ovarian cancer occur in the BRCA1 or BRCA2 genes. Typically, these genes help fight cancer by suppressing tumors. However, when they are mutated, it allows tumors to develop.

BRCA Mutation Statistics

About 50 out of 100 women with a mutation in one of the BRCA genes will get breast cancer by the time they are 70. This is in contrast to 7 out of 100 women in the general U.S. population who will get breast cancer.

Some groups are at a higher risk of BRCA mutations. One in 40 women of Ashkenazi-Jewish heritage has a BRCA gene mutation.

If genetic testing shows you have a mutation in one of the BRCA genes, your healthcare provider may recommend more frequent monitoring. They may also talk with you about preventative surgeries and medications.

Breast Density

Breasts are made of glandular, connective, and fatty tissue. Glandular tissue is the part of the breasts that makes milk, while connective tissue holds the breasts in place. Those with dense breasts have less fatty tissue.

About 43% of women aged 40 to 74 have dense breast tissue, and women with dense breasts are at higher risk of developing breast cancer. Further research is needed to determine the exact cause.

Lastly, mammograms of dense breasts are harder to read and interpret than those of fatty breasts. Dense breast tissue and lumps both show up white on a mammogram, making it difficult to tell the difference.

Mammograms and Dense Breasts

In addition to the increased risk of cancer with dense breasts, mammograms are harder to read in such women.


While obesity and dense breasts increase the risk of breast cancer, there is no scientific evidence that breast size does. 

Being a woman and getting older are two significant risk factors. Family history, genetic mutations, dense breasts, and alcohol intake can also increase risk. Those with a mutation in the BRCA1 or BRCA2 have a 50% chance of developing breast cancer than those who do not have the mutation.

A Word From Verywell

Having an increased risk for breast cancer can be overwhelming and scary. If you have any of these risk factors, talk with your healthcare provider. They may discuss the possibility of earlier mammograms or other imaging studies. Depending on the risk factor, they may also talk to you about genetic testing, preventative surgeries, or medications. 

Many of these factors are beyond your control. However, you decrease the risks within your control by eating well, exercising, and avoiding smoking or excessive alcohol.

Frequently Asked Questions

  • Are people with small breasts less likely to get breast cancer?

    There is no evidence that those with smaller breasts are less likely to develop breast cancer. 

  • What is the biggest risk factor for breast cancer?

    Gender and age are the biggest risk factors for breast cancer. Over 70% of those diagnosed are women who are 50 years or older.

  • Does breast size affect breast cancer outcomes?

    There is no scientific evidence that links poor breast cancer outcomes and breast size. However, there is evidence that obesity at diagnosis or excessive weight gain after diagnosis can negatively impact outcomes.

18 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Brandi Jones, MSN-ED RN-BC
Brandi is a nurse and the owner of Brandi Jones LLC. She specializes in health and wellness writing including blogs, articles, and education.

Originally written by Lisa Fayed