Types and stages of breast cancer

Introduction to types and staging

Breast cancer is categorised by how it looks under the microscope, as well as by what stage the cancer is at.

By looking under a microscope, a pathologist can tell the type and grade of cancer cells and how quickly the cancer cells are growing. All of these factors help doctors to predict the probable outcome of the disease and act as a guide for what treatments they will recommend.

The two most common types of breast cancer are ductal (to do with the milk ducts) and lobular (to do with the milk lobules). Each type can be either invasive (cancers that spread to other parts of the body) or in situ (ones that don’t).

Less common forms of breast cancer include inflammatory, medullary, mucinous, papillary, tubular, and Paget’s disease.

In situ carcinoma

Ductal or lobular cancers that do not spread outside the duct or lobule are called in situ cancers (“in situ” means “in place”). These are pre cancers. But they can either develop into invasive breast cancer or raise your risk of getting invasive cancer.

Types of breast cancer

Ductal Carcinoma In Situ (DCIS)

“In situ” means “in place”. Ductal Carcinoma In Situ (or DCIS) is a cancer affecting the ducts inside the breast that hasn’t spread outside the ducts. It is a pre cancer, if left untreated a proportion of them will grow to full blown invasive cancer.

DCIS is generally treated with surgery (mastectomy) or combined surgery (partial mastectomy) and radiotherapy.

Lobular Carcinoma In Situ (LCIS)

LCIS is not even a pre-cancer but if present does signal an increased chance of developing invasive cancer in the future and a marker of disease. Often this in situ cancer does not need treatment. Instead regular breast exams and mammograms are used to monitor for early changes of developing breast cancer.

Invasive carcinoma

When ductal or lobular cancers spread into surrounding breast tissue, the cancer is called invasive. Most (90%) invasive breast cancers are ductal cancers.

Breast cancers do two things as they grow. They spread locally in the breast (invasive) and can send cells through the blood and lymph channels to other sites (metastasis).

Metastasis (spreading to other parts of the body) is also called secondary cancer.

Invasive lobular carcinoma is a cancer that has spread from the lobules to surrounding tissue. It is often found in several different places within the breast and sometimes in both breasts. It can be difficult to detect by physical examination or mammography.

Tumour size and spread

Doctors have developed a system to tell how advanced or serious a cancer is. It is called staging. It evaluates the size of the tumour, how aggressive the cancer cells look in the microscope, the number and location of cancerous lymph nodes, and whether the cancer has spread to other tissue or organs. Information collected in staging is used to determine the likely outcome of the disease and to develop a treatment plan.

Size is important because the smaller the tumour, the less likely it has spread beyond the breast and the better the chance for successful treatment. Small tumours are classified as two centimetres or less.

The spread of cancer is referred to as either local, regional, or distant. Local means that the spread of cancer is confined within the breast. Even if cancer is found in several places in the breast, it is still considered local. Regional means that cancer has spread to the lymph nodes, mainly to the axillary nodes under the arm. Distant means that cancer has spread to other parts of the body.

Determining lymph node status

Lymph node status is determined by a pathologist who examines any nodes under a microscope after they have been removed from the armpit during surgery. This procedure is called a standard axillary dissection and it is most often done during the surgery that removes a tumour from the breast. However it can be done as a separate procedure.

A new option for determining node status is a sentinel node biopsy in which only one to three nodes are removed. The sentinel node is the first lymph node draining from the breast. A dye or radioactive tracer is injected to determine which node is the sentinel node. A sentinel node biopsy has fewer side effects and studies have shown that the procedure can be an effective way to assess node status, especially when done by experienced surgeons.

If nodes contain cancer cells, they are called positive nodes and the pathologist counts the number of nodes with cancer and includes the number in a pathology report.

Staging cancer

The scale used to determine the stage of breast cancer is called TNM staging and ranges from stage 0 to stage IV. A higher stage indicates more severe cancer.

This chart gives a summary of TNM staging. T represents the size of the tumour in the breast, N indicates lymph node status, and M indicates metastasis.

Stage	(T) Tumour Size	(N) Axillary Lymph Nodes	(M) Metastasis
0	Tiny cluster of cancer cells in a breast duct (in situ)	No spread	None
I	Up to 2cm	No spread	None
II	Smaller than 2cm	Has spread to the axillary lymph nodes	None
	Between 2cm & 5cm	May or may not have spread to the axillary lymph nodes	None
	Larger than 5cm	No spread	None
III	Any size	Has spread to multiple axillary lymph nodes so that the nodes become attached to each other	None
	Larger than 5cm	Has spread to axillary lymph nodes	None
	Any size but cells have spread to skin or chest wall	May or may not have spread to the axillary lymph nodes	None
	Any size	Has spread to lymph nodes along breastbone and above/below collarbone	None
IV	Any size	May or may not have spread to the axillary lymph nodes	Has spread to other organs of the body or the skin and lymph nodes above the collarbone

Types and stages of breast cancer

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