Breast cancer is divided into five stages. Stages 0-2 are
considered "early", stage 3 considered
"advanced", and stage 4 "late". Staging
categories are important for predicting future prognosis, and
determine optimal treatment recommendations.
Stage 0 is DCIS, or ductal carcinoma in situ. Breast cancer
arises from the cells that line the milk ducts. When the cancerous
cells are still contained inside the duct, it is diagnosed as DCIS.
This can only be determined by a pathologist doctor looking at the
tissue under a microscope. In general, when the DCIS lesion is
small, there is no need to suspect cancer spread outside the
Stage 1 is invasive or infiltrating cancer. Here, the cancer
cells have broken through the duct wall and are found outside the
ducts as well. In this case, doctors need to determine whether the
cancer has spread to the lymph nodes. Stage 1 breast cancer must
be equal or smaller than 2 cm in its invasive component, AND have
no spread to lymph nodes. Often, the tissue removed at surgery
contain DCIS in addition to the invasive cancer. However, only the
dimensions of the invasive cancer count. If the patient needs to
have multiple surgeries and the invasive cancer is found at more
than one operation, usually the dimensions are added together to
arrive at the final size.
Stage 2 has two subcategories. In stage 2A, the invasive cancer
can be 2 cm or less and has spread to axillary (armpit) lymph
node(s), i.e. positive node(s). Also, the invasive cancer can be
as large as 5 cm, but has not spread to lymph nodes, i.e. negative
nodes. In stage 2B, the invasive cancer is between 2cm and up to 5
cm and has spread to nodes. Here, cancer may measure even larger
than 5 cm if it has not spread to nodes.
Stage 3 includes invasive cancer larger than 5 cm that has
spread to lymph nodes. Also, cancer of any size that heavily
involves the axillary lymph nodes to the point that these nodes
are bulky and stuck together or stuck to other structures in the
axilla (armpit) are in this stage. Tumor spread to lymph nodes
either above or below the clavicle bone, or to nodes underneath
the sternum (breast bone), also falls into this category.
Furthermore, if the cancer of any size is attached to the chest
wall (pectoralis muscle and/or ribs), it qualifies as stage 3.
Inflammatory cancer, where the skin of the breast is red and
swollen, is classified in this stage, regardless of size.
Stage 4 is invasive cancer found outside the breast and
axillary lymph nodes, or "metastatic" to distant sites.
At this stage, it does not matter how large the primary cancer in
the breast is. Nor does it matter whether axillary/clavicle/breast
bone lymph nodes have cancer or not. The most common sites for
metastasis for breast cancer are bone and liver, followed by lungs
and brain. Standard testing include bone scan and CT scan of the
chest, abdomen and pelvis. More recently, PET scan is often done
to look for cancer spread. Sometimes, a brain MRI or CT is also