Triple-negative breast cancer (TNBC), a subtype of breast cancer, is a rare, malignant breast disease that lacks receptors for the hormones estrogen and progesterone and the human epidermal growth factor (HER2) protein usually found in other breast cancers. An aggressive cancer, triple-negative breast cancer grows and spreads more quickly than other types of invasive breast cancer. Triple-negative breast cancer is also more likely to reoccur and has a worse outcome (prognosis) than other breast cancers.
Triple-negative breast cancer accounts for 10-15% of all breast cancers and is more common in women under the age of 40 who are African American or Hispanic, and who carry the BRCA1 gene mutation. Seventy percent of breast cancers in individuals with a BRCA gene mutation are triple-negative.
Triple-negative breast cancer is classified in the following stages:
Stage 0 – Ductal cancer in situ (DCIS), which is a non-invasive breast cancer. The cancer cells are still located in a breast duct and have not spread.
Stage 1A – The breast cancer tumor is 2 centimeters or smaller and has not spread.
Stage 1B – The tumor is 2 centimeters or smaller (or undetectable) with microscopic spread (micrometastases) into one-to-three axillary (underarm) lymph nodes. The metastasis is more than .2 millimeters but less than 2 millimeters and has not spread to other parts of the body.
Stage IIA – One of the following has occurred, and the cancer has not spread beyond the lymph nodes: 1) The tumor is 2 centimeters (or undetectable) and has spread to one-to-three axillary (underarm) lymph nodes, with the cancer in the lymph nodes greater than 2 millimeters; 2) the tumor is 2 centimeters or smaller (or undetectable) and microscopic cancer is found in the internal mammary (breast) lymph nodes; 3) the tumor is 2 centimeters or smaller (or undetectable) and has spread to one-to-three axillary (underarm) lymph nodes and the internal mammary (breast) lymph nodes; or 4) the tumor is greater than 2 centimeters but less than 5 centimeters, but has not spread to lymph nodes.
Stage IIB – One of the following has occurred, and the cancer has not spread beyond the lymph nodes: 1) the tumor is larger than 2 centimeters but less than 5 centimeters and has spread to one-to-three axillary (underarm) lymph nodes, and microscopic cancer is found in the internal mammary (breast) lymph nodes; or 2) the tumor is larger than 5 centimeters but has not invaded the chest wall or skin.
Stage IIIA – One of the following has occurred, and the cancer has not spread beyond the lymph nodes: 1) the tumor is less than 5 centimeters (or undetectable) and has spread to four-to-nine axillary (underarm) lymph nodes; or 2) the tumor is greater than 5 centimeters, has not invaded the chest wall or skin, but has spread to one-to-nine axillary (underarm) lymph nodes or internal mammary (breast) nodes.
Stage IIIB – The tumor has invaded the chest wall or skin, but hasn’t spread to other parts of the body, and one of the following has occurred: 1) the tumor has not spread to the lymph nodes; 2) the tumor has spread to one-to-three axillary (underarm) lymph nodes, and microscopic cancer has spread to the internal mammary (breast) nodes; or 3) the tumor has spread to four-to-nine axillary (underarm) lymph nodes, or it has caused swelling in the internal mammary (breast) nodes.
Stage IIIC – The tumor is any size (or undetectable), had not spread beyond the lymph nodes, and one of the following has occurred: 1) the cancer has spread to 10 or more axillary (underarm) nodes; 2) the cancer has spread to the lymph nodes under the clavicle (collar bone); the cancer has spread to the lymph nodes above the collarbone; 3) the cancer has spread to axillary (underarm) lymph nodes; or 4) the cancer has spread to four or more axillary (underarm) lymph nodes, and microscopic cancer is found in internal mammary (breast) lymph nodes.
Stage IV – The cancer is any size and may or may not have spread to close lymph nodes, but it has spread to organs such as the liver, lung, brain, or bones, or other distant lymph nodes.