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This is an essential step in the diagnosis of cancer. It consists of a microscopic examination of a sample of the cancerous tumor obtained by biopsy. It confirms the malignancy of the lesion and specifies the type and grade of cancer.
The grade of a tumor is established in accordance with several microscopic criteria in the examination of a cancer cell, including differentiation.
The similarity of cancer cells to their originating tissue is more or less faithful. This level of similarity defines the degree of differentiation that determines the grade of the tumor.
A cancer is called “well-differentiated” if the resemblance is very close to the tissue of origin and conversely, “poorly differentiated” or “undifferentiated” if its appearance is very different.
In general, the higher the grade of the tumor, the more rapid its progression. The lower the grade, the slower and more local the progression.
The grades for several cancers range from 1 to 3. For others, it may be from 1 to 4 or from 1 to 5, and corresponds to the degree of cell differentiation.
The various types of cancers are determined by histology, i.e. the nature of the tissue in which they develop.
The following chart illustrates the different types of cancer according to the tissue in which they originated:
Epithelium (gland surface tissue)
85% of all cancers
Breast, liver, kidneys, prostate, ovaries, thyroid, colon, stomach, salivary gland, lungs, etc.
Squamous cell carcinoma
Squamous epithelial cell (skin, mucous membranes, skin)
85% of all cancers
Skin, gastrointestinal tract, lungs, head and neck (larynx, pharynx, oral cavity), cervix, etc.
Supporting or musculoskeletal tissue (bone, muscle, connective and fatty tissue, etc.)
2% of all cancers
Bone, cartilage, fatty tissue, vessels, etc.
B or T lymphocytes, cancer characterized by the presence of large, atypical cells
5-7% of all cancers
Lymph nodes, spleen
B or T lymphocytes
5-7% of all cancers
Lymph nodes, gastrointestinal tract, skin, brain, bones, genitals, lungs, etc.
Bone marrow cells (blasts)
4% of all cancer
Bone marrow cells (plasma cells)
4% of all cancer
Source (in French only): Cancer for Dummies
Sometimes cancers are simply designated according to the location in the body where they originated, e.g. breast cancer or prostate cancer.
Most benign tumours and some malignant tumours have the “oma” suffix at the end of their name.
When a malignant tumor has the same name as a benign tumor, the word carcinoma or sarcoma is added to the end of the name to specify that it is cancerous.
There are exceptions: lymphoma and melanoma are always cancerous; the word “malignant” is often added to them.
Cancer staging consists of determining the level of severity of the disease by means of clinical and complementary diagnostic tests. The aim is to detect the presence of visible metastases.
Besides the clinical examination, which is essential, it relies on complementary examinations such as medical imaging, nuclear medicine and blood tests.
Staging provides the physician with an accurate description of the disease that allows him to classify it within a clinical classification system.
What is TNM?
The TNM staging system for solid tumors was developed by the Union for International Cancer Control (UICC). It is the staging system most commonly used in oncology. This type of classification ensures that physicians share a universal vocabulary for talking about cancer.
T for tumour
N for node
M for metastasis
The primary tumor is defined as a function of its size and its extension to the surrounding tissues and is classified from T0 to T4.
Nodes are classified according to their number, size and local extension. They are ranked N0 to N3.
Metastases are classified according to their absence or presence and ranked M0 to M1.
The letters ABC may be added to the figures to describe the extent of the tumor more precisely. Example: T1aN0M0.
Certain tumors may be classified Tis, meaning “in situ.” These tumors are in their early stages of development, before they become invasive.
Although the basic classification remains the same, each type of solid cancerous tumor has its own TNM staging system.
Depending on the natural history of certain types of cancer, there are other classification systems that define the stage more precisely. Among these are systems for classifying melanoma, gynecological cancers, blood cancers and colorectal cancers.
What is a stage?
A stage represents the extent of a cancerous tumor.
There are 4 stages that generally rely on the TNM and that can be described as follows:
- Stage 1 corresponds to a single, small tumor (e.g. T1N0M0)
- Stage 2 corresponds to a larger local volume (e.g. T2N0M0)
- Stage 3 corresponds to an invasion of the lymph nodes and/or surrounding tissue (e.g. T1N1M0 or T3N0M0)
- Stage 4 corresponds to a wider spread to other organs and/or throughout the body by metastasis (e.g. T2N1M1 or T4N0M0)
Once the type and grade of the cancer have been identified, the rest of the staging allows the prognosis of the disease and the treatment plan to be defined.
A prognosis is a forecast or evaluation made by a physician, to the best of his abilities, regarding the likely impact cancer will have on a person. Survival statistics are among the tools used by physicians to establish a prognosis for a person with cancer.
The prognosis, essentially based on the illness’ general evolution, should be viewed as an indication rather than a verdict. Each person is different. If you have been diagnosed with cancer, we recommend that you discuss your prognosis with your physician.
The prognosis depends on many factors, depending on:
· the person’s medical history;
· the type of cancer;
· the stage of the cancer;
· the characteristics of the cancer;
· the treatments selected;
· the reaction to therapy.
Only a physician with a good understanding of these factors can examine all available data, alongside survival statistics, to ultimately make a prognosis. This physician is also the best person to answer questions regarding the type of future a person with cancer can aspire to.
For more information, call our Info-cancer Hotline: 1-800-363-0063.