Pathology test

This is an essential step in the diagnosis of cancer. It consists of a microscopic examination of a sample of the cancerous tumour obtained by biopsy. It confirms the malignancy of the lesion and specifies the type and grade of cancer.

Cancer Grade

The grade of a tumour 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 tumour.

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 tumour, 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 lower the differentiation, the lower the grade.
  • The higher the differentiation, the higher the grade.
  • A large tumour may sometimes contain cells of different grades.

Histological Classification

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:

 
Main types of cancers Tissue of origin of tumour Frequency (estimate) Locations
Adenocarcinoma 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.
Sarcoma Supporting or musculoskeletal tissue (bone, muscle, connective and fatty tissue, etc.) 2% of all cancers Bone, cartilage, fatty tissue, vessels, etc.
Hodgkin Lymphoma B or T lymphocytes, cancer characterized by the presence of large, atypical cells 5-7% of all cancers Lymph nodes, spleen
Non-Hodgkin Lymphoma B or T lymphocytes 5-7% of all cancers Lymph nodes, gastrointestinal tract, skin, brain, bones, genitals, lungs, etc.
Leukemia Bone marrow cells (blasts) 4% of all cancer Blood
Myeloma Bone marrow cells (plasma cells) 4% of all cancer Bone marrow
Source: 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 tumour has the same name as a benign tumour, 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.

Staging

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, 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 tumours 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 tumour 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 tumour more precisely. Example: T1aN0M0.
 
Certain tumours may be classified Tis, meaning “in situ.” These tumours are in their early stages of development, before they become invasive.

Although the basic classification remains the same, each type of solid cancerous tumour 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 tumour.

There are 4 stages that generally rely on the TNM and that can be described as follows:
  • Stage 1 corresponds to a single, small tumour (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.

For more information, call our Info-Cancer Hotline: 1 800 363-0063 FREE.

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