Determining Extent of Disease

There are two ways of classifying the stage of disease: clinical and pathological.  Clinical stage is based upon physical examination, mammography, and other imaging studies.  Examination of biopsy specimen determines the pathologic stage.  Sometimes surgery to remove breast cancer and nearby lymph nodes must be performed to determine the final pathologic stage.

 

Stage

The American Joint Committee on Cancer (AJCC) developed a system for classifying the different stages of cancer.  This system categorizes the tumor (T) in regards to size and type of infected tissue. The system also considers whether cancer has spread to nearby lymph nodes (N) and metastasis has occurred.  The overall stage of breast cancer is derived from the TMN classification.

If there is no spread to lymph nodes the cancer is described as node-negative, while node-positive classification is used for disease that has spread to the lymph nodes.  For node-positive cases, it is important to determine the number and location of involved nodes.  The farther away the affected nodes are from the breast the more extensive the disease.  The subclasses of positive nodes according to size and location are called N2 and N3, respectively.

 

Table 1: American Joint Committee on Cancer System (AJCC) for Classifying a Breast Cancer Tumor (T)

 

*T1 subcategories (mic, a, b, and c) are based according to sizes between 0.1 cm and 2cm.  T1mic (microinvasion) refers to cases of limited number of cancer cells present in the breast tissue.  There are four T4 subcategories (a-d), which refer to characteristics corresponding to different prognoses.

Table 2: American Joint Committee on Cancer System (AJCC) for Classifying Breast Cancer Spread to Lymph Nodes (N)

 

 

The M category describes evidence of distant metastasis:

 

* Mx: no metastasis detected

* M0: no distant metastasis

* M1: distant metastasis

 

Imaging studies are used to confirm metastasis, which is most common in the lungs, bone, and the liver.  Physicians can detect metastasis through chest x-ray, bone scan, and computed tomography (CT) or MRI of the abdomen.  When a physician believes cancer has spread, but is not sure to which part of the body, a positron emission tomography (PET) maybe used.

Breast cancer can vary according to how extensive the disease has progressed.  Physicians classify breast cancer in different stages ranging from 0 to IV.  If the breast cancer is noninvasive, isolated to only the ducts or lobules (Tis), then the cancer is in Stage 0.  These would include DCIS and lobular carcinoma in situ (LCIS).  Stage I breast cancer refers to cancer that is small (T1) which has not spread to the lymph nodes (N0).

Stage II of breast cancer is divided into two subdivisions.  Stage IIA breast cancer refers to one of several cases.  Stage IIA can describe when tumor may be small (T1) but has spread to the axillary lymph nodes (N1), located in the underarm.  This stage can also describe a larger tumor (T2) that has not yet spread to the lymph nodes (N0).  If there is no evidence of a tumor in the breast (T0) but cancer cells in the axillary lymph nodes (N1) are present, then stage IIA classification may also be used.  Early stage breast cancers are described as stage 0, I, or IIA.

Stage IIB and stage III classifications describe later stage cancer.  When a medium-size tumor (T2) spreads to three or less axillary lymph nodes (N1), then the disease is a stage IIB cancer.  A large tumor (T3) that is not present in the lymph nodes (N0) is also stage IIB.

Stage III breast cancer is subdivided into three different subclasses, IIIA, IIIB, and IIIC.  A tumor that is smaller than 5 cm (T1 or T2), which has spread to axillary lymph nodes (N2), is classified as stage IIIA.  If the tumor is larger than 5 cm (T3) and has spread to lymph nodes (N1 or N2) it is also classified as stage IIIA.  Tumors with swelling, ulceration, inflammatory breast cancer, and that have spread into the chest wall (T4) is characterized as stage IIIB.  Extensive spread to lymph nodes (N3) from a tumor of any size and extension is classified as stage IIIC.

 

Metastasis (any T, any N, M1) of breast cancer is refers to advanced disease and is classified as stage IV.

 

Grade

The breast cancer's grade is based upon how closely the breast cancer cells resemble normal breast cells and how they are arranged in relation to each other.  Other characteristics are also considered.  Grades 1, 2, or 3 are assigned based upon an evaluation by a pathologist.  Tumors with slower growth and with smaller likelihood of spreading are lower in grade, while a higher grade tumor is faster growing and more likely to spread.  Low-grade tumors, which are small and have not spread to lymph nodes, may not need additional treatment, besides complete removal.