In smear, endoscopy, or biopsy reports, doctors sometimes note the presence of metaplasia. This can be squamous, intestinal, bony, etc. Should we be worried? Not necessarily. Some metaplasias are normal, others can progress to cancer over the years, and therefore require regular monitoring.

Metaplasia is the transformation of differentiated cellular tissue, typical of the organ observed, into another differentiated cellular tissue, which exists elsewhere but should not be there. For example, the cells lining the cervix can take on all the characteristics of a vaginal lining, or the inner lining of the stomach can locally transform into intestinal epithelium. It is a natural defense mechanism of tissues against prolonged or repeated aggression (by bacteria, virus, inflammation, etc.).

Normally the process is reversible. The tissues return to their original shape when conditions become favorable again. But, sometimes this is not the case, either because the cause of the aggression is still there, or because the metaplasia is too installed. This then becomes pathological. Regular monitoring is necessary to ensure that it does not turn into cancer over time. This will not necessarily be the case, but good monitoring allows early and appropriate management of lesions if they occur.

All tissues in the human body can be affected by metaplasia, except nervous or muscle tissue. The most frequently encountered forms are squamous metaplasia, intestinal metaplasia and bone metaplasia.

The malpighienne métaplasie

This term is used when a tissue having a very specific function is transformed into squamous epithelium, that is to say into a covering wall, protective and resistant, such as one finds at the level of the skin, the vagina or the skin. ‘esophagus. This form of metaplasia is found in particular:

• at the level of the cervix : the walls of the uterus and the vagina are in the continuation of one another, and the junction zone between the two can move slightly according to the hormonal variations. A vaginal infection can also be involved. There is therefore not necessarily something to worry about when faced with the presence of squamous metaplastic cells at the entrance to the cervix. It is more worrying if this transformation concerns a larger area and is associated with the presence of a human papillomavirus (HPV, or HPV in English). These viruses are in fact known to promote cancers of the cervix;
• in the bronchi : chronic exposure to tobacco smoke and / or other toxic fumes leads the bronchial mucosa to transform into squamous epithelium, which is more resistant. This metaplasia is not immediately dangerous, but there is a risk of transformation into a cancerous lesion later.

Intestinal metaplasia

This time it is a transformation of the tissues into intestinal epithelium. This can happen:

• in the stomach : in chronic gastritis, especially if the overproduction of gastric acid is linked to an infection by the bacterium Helicobacter pylori (H. pylori), the stomach lining reacts by adopting the structure of a more resistant intestinal wall . Even if the bacteria is completely eradicated, this gastric intestinal metaplasia (IGM) can persist and evolve over time into a cancerous lesion;
• in the esophagus : in gastroesophageal reflux disease, the lining of the lower esophagus is chronically exposed to the acidic pH of gastric fluid. As a reaction to the inflammation caused, it can gradually transform into the intestinal lining. This metaplasia, also called endobrachyesophagus (or Barette’s esophagus), must be detected quickly, in order to avoid the spread of metaplasia in the esophagus and its repercussions (difficulty in swallowing, etc.). The situation only degenerates into cancer in 0,33% of cases.

Bone metaplasia, or osteoid

Following a miscarriage, voluntary termination of pregnancy (abortion) or childbirth, embryonic tissue may remain in the uterus, which may continue to develop there in the form of bone tissue. This complication is rare, but can cause secondary infertility, if not taken care of. It is usually diagnosed in time, looking for the cause of persistent bleeding. The calcifications are then removed.

The causes of metaplasias are diverse: infection by bacteria or viruses, tobacco, respiration of carcinogenic products, etc. All cause tissue inflammation such that the latter react by transforming into another tissue, better equipped to resist aggression.

Abnormal metaplasias do not have any specific symptoms. Either they are asymptomatic and appear during an organized screening (a smear, for example), or they are associated with symptomatic pathologies which, such as chronic gastritis or gastroesophageal reflux, lead doctors to order an endoscopy ( also called bronchoscopy, gastroscopy or hysteroscopy depending on the organ to be explored) with, if necessary, a biopsy. The diagnosis can only be made by observing the tissues up close.

Strictly speaking, there is no treatment for metaplasia. If the situation does not recover on its own, it is not immediately serious, but it should be prevented from spreading or escalating. That is why the cause must be eradicated. An antibiotic treatment will for example be prescribed by the gastroenterologist in the event of infection of the stomach by H. pylori, associated with an anti-acid treatment against gastritis.

Then, regular monitoring, every year to every three years depending on the case (location of the metaplasia, age, family history, etc.), will be necessary. It will consist of an endoscopy with biopsies, to verify the absence of a precancerous lesion. 

Metaplasias, especially in the stomach and bronchi, increase the risk of gastric cancer (+ 5%) or lung cancer. However, these pathologies require early treatment.