Breast cancer is a malignant disease caused by an uncontrolled growth of cells in the breast. Improvements in prevention and diagnosis have resulted in earlier diagnosis and treatment. Patients, both men and women, should be aware of symptoms that include: a new lump or mass, swelling of all or part of a breast, skin irritation or dimpling, breast or nipple pain, nipple retraction, redness, scaliness, thickening of the nipple or breast skin, or a nipple discharge (other than breast milk).

When a physician suspects breast cancer, a biopsy is usually requested. During the procedure, a sample of breast tissue is collected to be analyzed under a microscope. After confirming the diagnosis, the cancer care medical team will define a treatment plan and make a prognosis. In order to accomplish move through the correct treatment, physicians classify the individual breast cancer according to standard parameters that include type, grade, stage, and gene expression of the breast cancer.

Classification Based on Breast Cancer Type

The tissue analyzed during a biopsy can reveal the presence of cancer and if it is carcinoma or another type, such as sarcoma.

Types of cancer are usually classified based on the location and aggressiveness of the disease.

The most common type is ductal carcinoma, which means the original site of the disease is within the ducts (tubes) that transport milk to the nipple. The cancer can be classified as in situ (DCIS) which means it is not invasive and is contained inside the duct, or as an invasive breast cancer if it has spread outside the duct.

Additional breast cancer types include: triple negative breast cancer, inflammatory breast cancer, metastatic breast cancer, and other rare forms of breast cancer.

Classification Based on Breast Cancer Grade

Pathologists also classify the disease by grade. The grade is defined according to the appearance of the tissue on the biopsy – how closely it looks compared to healthy tissue, and how fast the cancer cells divide. A lower grade usually means that the cancer grows slower and is less likely to metastasize, but a higher grade refers to a faster cancer growth with more probability of spreading.

The histologic tumor grade can also be called Bloom-Richardson grade, Nottingham grade, Scarff-Bloom-Richardson grade, or Elston-Ellis grade, and can be communicated with words or numbers. Grade 1 means well differentiated (looks most like normal cells), while grade 2 means moderately differentiated. Grade 3 refer to poorly differentiated breast cancer (almost unrecognizable and fast growing.)

Classification Based on Breast Cancer Stage

The stages of breast cancer refer in numbers to the extent and evolution of the breast cancer, but terms like “locally advanced” or “regionally advanced” may also be used. In stage 1, patients usually have invasive breast cancer, while 1A refers to a tumor smaller than two centimeters that has spread to the lymph nodes but not outside the breasts, and 1B to isolated cancerous patches rather than a mass that measures 0.2 to two millimeters. Non invasive cancer, though cancer, is concidered stage 0 (zero).

Stage 2 is when the tumor has spread to the auxiliary lymph nodes, which can be two to five centimeters and remain localized (2A) or measure two to five centimeters and 0.2 to two millimeters of metastasis.

Stage 3 describes a more aggressive form of invasive breast cancer and is divided into three sub phases. Stage 4 indicates the that the cancer has spread to other organs of the body such as the lungs, the liver, distant lymph nodes, skin, or bones.

Breast Cancer Classification Based on Gene Expression

According to the American Cancer Society, gene expression is an additional, and fairly new way, to classify breast cancer. Based on molecular features determined by a PAM50 test, gene expression divides breast cancers into four groups.

Luminal A and luminal B breast cancer types have gene expression patterns similar to healthy cells. Luminal A cancers are low-grade that grows slowly. Luminal B cancers are faster-growing and more aggressive.

HER2 breast cancer type is diagnosed in the presence of additional copies of the HER2 gene.

The basal type, among the triple negative types,  is diagnosed in the presence of a lack of estrogen or progesterone receptors but normal levels of HER2. It is more common among women with the BRCA1 mutation. For reasons unknown, basal cancer is more common among African-American and younger women.


Note: Breast Cancer News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.