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A cancer diagnosis is based on the results of examinations complementary to screening. This diagnosis allows the doctor to propose a treatment that is right for you, that is based on the type of cancer, the progression of the disease (its stage) and its degree of aggressiveness (its grade).

The doctor must first determine whether the health problem appearing in the breast(s) is in fact cancer and not a different disease. Moreover, if it is breast cancer, its type and stage must be ascertained before choosing, among possible treatments, the one or ones most likely to succeed, as well as the appropriate dosage.

Diagnosis is required for women:

  • who have signs of breast cancer;
  • whose doctor believes they may have breast cancer, after discussing their health issues with them and having performed a clinical breast examination;
  • who have had a screening mammography that seems to indicate there is a problem with one or both breasts.

Other tests besides mammography, described below, may have to be performed to accurately determine all aspects of the diagnosis: understand the nature of the problem, and if the disease is confirmed, determine its stage, that is to what extent the cancer has spread, as well as check the woman’s general state of health to properly plan for her treatment.

Diagnostic Tools

Following are the main tests, besides mammography, that are used to make an accurate breast cancer diagnosis:

  • clinical breast examination: palpation of the breasts and examination of the underarms by a doctor;
  • complementary radiology films: additional mammographies to better determine the nature of the lesion;
  • ultrasonography: a test that uses sound waves, mainly to determine the presence of cysts in the breast;
  • non-surgical biopsy: taking cell or tissue samples using different kinds of needles;
  • surgical biopsy: obtaining a sample of the lesion through an operation;
  • stereotactic localization: a procedure whereby a wire is inserted into a non-palpable lesion, using a computer. This wire serves as a guide to surgically retrieve a sample at the exact spot where the lesion is found.

Breast Ultrasonography and Other Imaging Techniques

During a breast ultrasonography, high-frequency sound waves are projected onto the solid parts of the body, without penetrating through them.

Since healthy breasts are made up only of soft tissues and fluids, while tumours can appear as solid masses, the breast ultrasonography reveals the tumours, and makes it easier to understand their nature. Your doctor may recommend this test in order to:

  • examine any mass or anomaly detected in a breast through clinical breast examination or mammography;
  • determine whether a tumour is solid or if it is a cyst filled with fluid;
  • accurately pinpoint the part of the breast where the problem is located to plan for a biopsy.

How is a breast ultrasonography carried out? The test can be performed in a doctor’s office, at a clinic or hospital, and as an outpatient procedure. The test can be expected to last 15 to 30 minutes, sometimes more, as the case may be.

The woman lies on an ultrasound table while a technologist applies a special gel to the skin of the area to be examined. This cool, slippery gel is a lubricant that improves the transmission of the sound waves. Next, a health professional moves a transducer—a probe resembling a microphone—directly over the skin. The high-frequency sound waves emitted by the transducer are reflected as echoes, analyzed electronically, and then rendered as images on a screen.

Generally a woman can resume her daily activities after a breast ultrasonography, as no anesthesia is required and the test causes no pain or side effects.

Other Imaging Techniques

Besides breast ultrasonography, other techniques are used to obtain breast tumour images and information on its progression, to determine specifically whether the cancer has spread to other parts of the body. Most of these tests do not require anesthesia and do not cause pain.

Radiography is used, of course, among a wide range of techniques such as computerized axial tomography (CAT scans), ductography, breast scintigraphy, bone scan, magnetic resonance imaging (MRI), as well as ultrasonography or radiography of organs other than the breasts. Click here to learn more about other imaging techniques.

Magnetic resonance imaging (MRI) is, more specifically, an imaging test using radio waves and a powerful magnetic field to show contrasts within the tissues. Certain contraindications exist, but there are no known harmful effects.

Used mainly to detect the presence of metastasis and to help choose a treatment, this imaging technique can be an important complement to mammography, when used as a screening tool in certain groups of women, notably those with a BRCA gene mutation.


A definitive cancer diagnosis can be obtained only through a breast biopsy. During a biopsy, cell or tissue samples are taken from one or both breasts and examined in a laboratory where the presence or absence of cancerous cells is ascertained.

A breast skin biopsy can also be performed if an inflammatory breast cancer is believed to be present; a biopsy of the nipple is performed when the problem is believed to be Paget’s disease.

There are in fact several types of breast biopsies; your doctor will choose one according to the type of abnormal breast mass. Certain biopsies require imaging techniques and local or general anesthesia, while others do not.

Laboratory Tests

When a biopsy reveals cancerous cells, it is often necessary to conduct further analysis of the samples in a laboratory setting to better understand the state of the breast cancer and then plan the best possible treatment. Hormone receptor status analysis of the tumour, HER2 gene test, and blood tests are among the main laboratory tests available.

Hormone receptor status analysis of the tumour. The hormones linked to breast cancer, that are in a woman’s body—estrogen and progesterone—bind to structures called receptors in the cells or on their surface. These hormones can affect cell behaviour or growth. Consequently, analyzing the status of the tumour’s hormone receptors helps to determine:

  • how the tumour will progress;
  • whether the tumour can be treated with hormonotherapy;
  • other treatments that could be effective, if hormonotherapy proves not to be.

Analysis of HER2 gene status. HER2 is a protein produced by a mutated gene that can promote tumour growth (an oncogene). Certain cancerous breast cells contain an excessive amount of HER2, in which case the tumour is termed HER2-positive. Analyzing the status of this gene makes it possible to evaluate the amount of HER2 produced by the tumour, and to help doctors establish the most appropriate treatment plan.

Blood tests. In certain cases, blood tests may be necessary to determine the quantity and appearance of various kinds of blood cells. The results provide indications as to whether the breast cancer is present or not, and if it is, whether or not it has progressed and spread to other parts of the body. This allows doctors to determine if the organs of a person affected with breast cancer are functioning normally.

Stages and Grades of Breast Cancer

Once all necessary tests have been completed and have led to an accurate diagnosis of breast cancer, the stage and grade of the disease must be determined in order to identify the most appropriate treatment.

  • Staging means defining the size of the tumour and determining whether it has developed outside of the breast and spread to other parts of the body. There are five stages of breast cancer, from 0 to 4 (see table below).
  • Grade (histologic classification) is the anticipated degree of development of the disease. The grade is determined by analyzing the appearance and behaviour of the cancerous cells, and comparing it to normal cells. 


The TNM classification—for Tumour, lymph Nodes, and Metastasis (spread of breast cancer cells that formed new tumours in other parts of the body)—is used most frequently to determine the stage of breast cancer. This classification takes into account:

  • the size of the primary tumour (at the onset);
  • the number of regional lymph nodes containing cancerous cells, and their location;
  • the spread of the cancer (metastasis) to other parts of the body.

At the first two stages, 0 and 1 of breast cancer, cancerous cells are found only in the lactiferous ducts or lobules. They have not spread to the lymph nodes or to other parts of the body. This cancer is called “in situ”. 

At the next three stages, 2 to 4, cancerous cells have spread outside the lactiferous ducts and the lobules. The cancer is thus considered “invasive”. However, if screened early, it can be treated successfully.

The Five Stages of Breast Cancer

State Description


Cancer cells are found only in the membrane of a milk duct (called ductal carcinoma in situ, DCIS) or in the membrane of a lobule (called lobular carcinoma in situ). 


The cancer tumour is less than 2 centimentres in size and the cancer has not spread outside the breast. 


The tumour is between 2 and 5 centimentres in size, or the cancer has spread to neighbouring lymph nodes, or both. 


The cancer has spread to lymph nodes and possibly to neighbouring tissues, such as muscles or skin. 


The cancer has spread to other parts of the body. 



Examining a biopsy sample through a microscope makes it possible to determine the grade of breast cancer, that is, how fast it is growing and what treatment should be proposed based on these facts.

The Three Grades of Breast Cancer

Grade Description


Low grade: Growth is slow and the risk of spreading is lower. 


Intermediate grade: Growth rate and risk of spreading are moderate.


High grade: Growth is faster and the risk of spreading is higher.