Breast cancer occurs when cells in the breast become abnormal and grow out of control. One of the most well-known symptoms is a palpable breast lump, but breast cancer does not always cause a lump in the breast. There are several breast changes women should be checking for regularly that may be a sign of breast cancer.
12 Breast Cancer Symptoms
The Know Your Lemons Foundation created a campaign using a box of lemons modified to represent 12 signs of breast cancer that all women should be aware of. The 12 signs of breast cancer include:
- Swelling or thickening of the breast
- Dimpling of the breast skin
- Nipple crust
- Redness or heat of breast skin
- New nipple discharge that is not breast milk, including blood
- Skin sores
- Bumps
- Growing veins on the breast
- Sunken nipple
- Changes in the size or shape of the breast
- “Orange peel” skin
- Hard lump in the breast
Other signs and symptoms of breast cancer may include:
- Skin changes on the breast: scaliness or flaky skin
- Pain in any area of the breast
- Nipple pain
- Lump in the underarm area (armpit)
What Causes Breast Cancer?
It is not known what causes breast cancer, but risk factors are linked to the disease include:
- Being female
- Age over 55
- Inherited genes, including BRCA1 and BRCA2 and others
- Family history or personal history of breast cancer
- Overweight/obesity
- Alcohol use
- Physical inactivity
- Use of hormonal birth control
- Having a first child after age 30 or having no children
- Hormone replacement therapy (HRT) for menopause, particularly estrogen and progesterone (combined hormone therapy)
- Dense breast tissue
- Ethnicity: White women are slightly more likely to develop breast cancer during their lifetime, but African-American women are more likely to develop breast cancer under age 45
- Certain benign breast conditions
- Early onset of menstruation (before age 12)
- Menopause after age 55
- Radiation to the chest
How Is Breast Cancer Diagnosed?
Sometimes, a person may discover a lump or notice changes in the breast. A doctor will perform a physical exam to look for breast changes.
Tests used to confirm a diagnosis of breast cancer include:
- Mammogram (a special type of X-ray)
- 3D tomosynthesis is a special new type of digital mammogram
- Breast ultrasound
- Breast magnetic resonance imaging (MRI)
- Biopsy, in which samples of tissue from the breast are removed and examined
What Is the Treatment for Breast Cancer?
Treatment for breast cancer usually involves a combination of surgery, radiation, chemotherapy, and other treatments.
- Surgery
- Mastectomy: surgical removal of the entire breast
- Lumpectomy: removal of cancer and some tissue surrounding it
- Radiation therapy
- Chemotherapy
- Hormone therapy
- Targeted therapy
- Immunotherapy
From 
https://www.uptodate.com/contents/breast-cancer-the-basics?search=breast%20cancer&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1
https://www.uptodate.com/contents/breast-cancer-guide-to-diagnosis-and-treatment-beyond-the-basics?search=breast%20cancer&source=search_result&selectedTitle=8~150&usage_type=default&display_rank=8
http://www.cancer.org/cancer/breastcancer/overviewguide/breast-cancer-overview-what-causes
https://www.breastcancer.org/
https://knowyourlemons.org/