NCCN Guidelines for Patients™: Breast Cancer
Part 2: About my cancer
2.1 Breast growth
Before puberty, breasts of boys and girls are similar. Both
have nipples, areoles, and little fat. During puberty, girls
have increases in female hormones that boys do not.
These female hormones cause the growth of lobules,
milk ducts, and fat in the breasts of girls (Figure 2). Fat
and connective tissue give shape to the breast.
Breast cancer is the most common type of cancer in
women. In contrast, it is rare among men. In women, it
is second to lung cancer as the cause of cancer-related
death. Although more women have been diagnosed with
breast cancer in recent decades, fewer women have
died because of early diagnosis and better treatments.
The information in these guidelines is about breast
cancer in women.
Figure 2. Parts of the female breast
Derivative work of Breast Anatomy by Patrick J. Lynch and C. Carl Jaffe, MD available at
under a Creative
Commons Attribution 3.0 Unported license
• In girls, breasts grow during puberty to
be able to make milk for babies.
• Most breast cancer occurs in women.
It is the most common type of cancer
• It is not known what causes breast cancer.
• Breast cancer often starts in the milk ducts
or lobules and then spreads into the fatty
tissue of the breast.
• Starting at age 20, you should be
given screening exams to find breast