02 June 2022

Check up #2 - What are metaplasia, dysplasia and neoplasia?

Check Up is a new series of short texts through which we intend to offer cancer patients and their families (as well the interested general public), clear, to-the-point information related to Oncology, concerning topics and issues that are often causes of concern among the population, but frequently remain confusing and difficult to understand. Our goal is that the information published here will contribute to making the language used in Oncology more easily and quickly understood by all.

Check up #2 - What are metaplasia, dysplasia and neoplasia?

Metaplasia, dysplasia, neoplasia are three processes of cellular transformation.

Metaplasia occurs when a type of cell transforms itself into another normal cell type, as an adaptive response to adverse environmental conditions (for example, inflamation).

One example of metaplasia is so-called intestinal metaplasia, where cells of the most superficial layer of the lining of the stomach (the epithelium), transform themselves into cells that look like intestinal cells. In 99% of cases, intestinal metaplasia arises in the context of a chronic gastritis associated to infection by the bacterium Helicobacter pylori. 

In general, Metaplasia doesn’t evolve into cancer. It is considered a benign pre-neoplastic (see “neoplasia” below) condition that needs to be watched – and, if it shows signs of progression, removed. 

If the inflamation/infection is not controlled, metaplasia can evolve into dysplasia. Dysplasia is an initial state of the neoplastic process (see “neoplasia” below). 

A well-known example is cervical dysplasia, the growth of abnormal cells on the surface of the cervix (the canal that links the vagina to the uterus). It is associated to a sexually transmitted infection by a common virus, the Human Papillomavirus (HPV).

Mild dysplasia, in most cases, should not evolve into an invasive neoplasia (see below), but must nonetheless be regularly watched for progression (for example, through Pap smears). Severe dysplasia cases, on the other hand, may require surgery to remove the abnormal cells, followed by close surveillance.

I left untreated, dysplasia can progress to invasive neoplasia. This occurs when the accumulation of mutations in certain genes confers to the cells the capacity to multiply rapidly and continuously, thus eluding the body’s vigilance and control mechanisms. 

However, “neoplasms”, commonly known as tumours, are not always invasive, or malignant; they can be benign, when their growth is controlled and there is no dissemination to other tissues/organs, be they adjacent or distant.

So the first thing to do, in the presence of a tumor, is to determine which of these two classes it belongs to. Malignant tumours, those that have the potential to grow rapidly and spread throughout the body, are what we generally call "cancers". 

By Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.
Reviewed by: Rita Canas Marques and Inês Rolim, Anatomical Pathology
Sources include: Mayo Clinic, NCI Dictionary of Cancer Terms, National Library of Medicine, Healthline, Cambridge English Dictionary, Interview with Paulo Fidalgo
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