Cancer: what are the diagnostic tools ?

The diagnosis of cancer requires the performance of several clinical, biological and imaging examinations.

The clinical examination

The clinical examination conducted by the doctor is an essential step in the development of the diagnosis of cancer.

The doctor consulted examines the patient: he measures his pulse, his blood pressure, he listens to his breathing … A specific examination of the potentially affected region is also conducted: examination of the breasts, gynecological examination, examination of the mouth or throat. .. The clinical examination must be complete. Its purpose is not only to diagnose the presence of a tumor, but also to identify the possible presence of metastases. It allows in addition the possibilities therapeutic .

Biological examinations

A blood and / or urine assessment completes the first clinical assessment.

They make it possible to measure parameters relating to the general state of health of the patient, but also to measure the tumor markers which may be present. These markers are generally molecules formed in small quantities by normal cells but which are found produced in excess by tumor cells . Once passed through the bloodstream or the urine, these markers can be measured: their concentration is generally dependent on the number of cancer cells.

Please note, however, that tumor markers can sometimes be produced in excess during certain non-cancerous diseases. At the end of an assay of tumor markers, a high rate can only be interpreted after additional examinations, which will make it possible to identify its cancerous origin or not.

Some common tumor markers include:

  1. ace ( carcinoembryonic antigen ) , an abnormally high marker in patients with breast, colon, thyroid, lung, kidney, stomach, rectum, ovary … cancers
  2. the psa , prostate cancer marker;
  3. calcitonin , a marker for thyroid cancer.

Medical imagery

Medical imaging is a set of techniques for obtaining images of internal parts of the body.

Imaging techniques allow doctors to verify the presence of a tumor, its size, shape, metabolic activity and exact location. This information is useful for defining the treatments to be implemented and for assessing whether surgery can be offered.


It makes it possible to obtain an image using x-rays. Organs appear black or white depending on the ability of radiation to pass through. To observe certain organs, the injection of a so-called “contrast” product is necessary: ​​it allows them to be clouded in the image. The radiograph is particularly used in oncology to examine the chest, abdomen or breasts.


This is a method is based on the use of ultrasound, that is to say of imperceptible sound waves in the ear. The waves are sent through the skin towards the organ. The ultrasound, which has a constant speed, is reflected by the tissue they meet and returns to the emitting probe. Computer processing translates the time taken to cover this distance into images, making it possible to obtain an indirect representation of the region.

To observe certain organs, it is necessary to introduce the probe into a hollow organ, such as the vagina, rectum or esophagus. In this case, the probes used, called endocavitary , are much smaller.

The sensitivity of diagnostic techniques

During a clinical examination, the doctor cannot detect superficial tumors whose size is less than approximately 1 cm in diameter. At this point, the tumor contains approximately one billion cells. Medical imaging detects tumors 1 mm in diameter, or approximately 10 million tumor cells. The most sensitive tumor markers detect tumors containing around 100,000 cancer cells. The pathologist is able to detect a single tumor cell that will be visible under a microscope.

The scanner

He uses x-rays. The ray source moves around the patient to lead to the production of a series of several pictures representing the scanned area in section, on different thicknesses.
The sensitivity of the device also makes it possible to generate much more precise images than with a conventional radiography. The scanner is therefore often used to study an anomaly initially detected by radiography or ultrasound. It also facilitates the study of certain organs difficult to characterize by radiography (pancreas, liver, lung, spleen, bladder, kidney).

MRI or magnetic resonance imaging

It is a method of exploration based on the detection of reactions from different parts of the body exposed to a magnetic field. By the energy which it brings, the magnetic field directs in the same direction all the atoms of hydrogen which compose the fabrics. When the field is stopped, these atoms return to their initial state by restoring this energy. Not all body tissues have the same proportions of hydrogen. Also, the energy levels restored will be different from one organ to another. These are recorded by a computer which translates these differences into images by degrees of black and white which indirectly represent the organs explored.

The scintigraphy

It allows to visualize the functioning of an organ. It takes place in two stages: a weakly radioactive product, called a “tracer”, is injected into the patient. It attaches specifically to the organ to be observed. Then, a gamma-camera coupled to a computer records the radiation emitted by the tracer. A very precise cartography of the organ to be explored is obtained and can be reproduced at several time intervals.

PET-scan or “PET” for positron emission tomography

The PET-scan also makes it possible to visualize the functioning of the organs. It consists first of injecting labeled glucose, that is to say a weakly radioactive sugar, then of analyzing the image obtained by a scanner. Cancer cells are identifiable because they have more activity than healthy cells and therefore need more glucose to function. However, some tumors do not consume sugar and therefore cannot be observed by this method.


The biopsy makes it possible to confirm the diagnosis and to specify the nature of the cancerous lesion.

The biopsy is an essential examination when diagnosed with cancer. It alone confirms the diagnosis and specifies the nature of the cancerous lesion. In practice, the biopsy consists in taking a sample of suspect tissue to examine it by microscopy.
Tissue analysis is performed by an anatomo-pathologist. It is sometimes supplemented by a molecular characterization which aims to seek the specificities of the cells (including tumor markers) which form the tumor and to orient the prognosis and / or treatment.

Depending on the location of the tumor, the sample is taken by puncture, using a fine needle, or by endoscopy, using a probe fitted with an optical system and introduced into a hollow organ (intestine, bronchi , bladder ). In other cases, the biopsy is performed during a surgical intervention: the entire anomaly is then removed immediately to be subjected to analysis.

Extension assessment

The purpose of the extension report is to specify the state of progress of the disease.

When cancer is diagnosed, it is essential to know its progress. In particular, it is crucial to know whether the disease has spread to other organs. The purpose of the extension report is to answer these questions. It is established on the basis of the results of diagnostic examinations, sometimes supplemented by one or two additional examinations. Ultimately , this assessment allows the medical team to assess the stage of the disease according to the TNM classification and thus to determine the most suitable therapeutic strategy.

The stages of the disease

Malignant tumors are classified according to their stage of evolution thanks to the TNM system. This system takes into account the local evolution of the Tumor (T), its extension to the neighboring lymph nodes (N) and its possible dissemination in the form of Metastases. (M). For each of these three parameters, the tumor is characterized by a number indicating:

  • local invasion : from T1 to T4 depending on severity;
  • the number of regional lymph nodes invaded : from N0 (no lymph node affected) to N3 when many lymph nodes are affected;
  • absence (m0) or presence (m1) of metastases