Difference Between Metaplasia and Dysplasia

The main difference between metaplasia and dysplasia is that the metaplasia is the initial changes of normal cells to a different cell type whereas the dysplasia is the increased degree of disordered growth and maturation of a tissue. Furthermore, metaplasia is non-cancerous while dysplasia can be cancerous. 

Metaplasia and dysplasia are two types of cellular changes that occur due to various internal and external factors. 

Key Areas Covered 

1. What is Metaplasia
     – Definition, Causes, Examples
2. What is Dysplasia
     – Definition, Causes, Examples
3. What are the Similarities Between Metaplasia and Dysplasia
     – Outline of Common features
4. What is the Difference Between Metaplasia and Dysplasia
     – Comparison of Key Differences

Key Terms 

Cellular Changes, Dysplasia, Genetic Alterations, Malignancy, Metaplasia, Neoplasia, Stimuli

What is Metaplasia 

Metaplasia is the reversible process in which a well-differentiated cell type is replaced by another well-differentiated cell type of the same germline. It can be a normal physiological change in the cell type such as ossification of a cartilage into a bone. It can also be a response to an external stimulus such as the change of the respiratory epithelium of chronic smokers into squamous epithelium due to irritation. This means metaplasia involves a change in the cell type depending on the conditions of the body. 

Some other examples of metaplasia are: 

• The change of the cuboidal/columnar/transitional epithelium into stratified epithelium due to vitamin A deficiency; 
• The change of transitional cells into stratified squamous epithelium due to warm infestation or kidney stones; 
• The change of the squamous epithelium into columnar epithelium (Barrett’s esophagus) acid reflux; 
• The change of the glandular epithelium into squamous epithelium due to the low pH of the vagina. 
  

  Figure 1: Micrograph of Barrett’s Esophagus

Generally, metaplasia can return to the normal conditions when the stimulus is removed. However, some metaplasia conditions such as Barrett’s esophagus may be pre-cancerous. In addition, a metaplasia unaddressed for a considerable time period can become dysplasia and turn into cancer. 

What is Dysplasia 

Dysplasia is the disordered growth due to the loss of cellular uniformity as well as architectural organization, especially in the epithelium. It can range from low-grade to high-grade. Dysplasia is also reversible at the initial stage. However, dysplasia shows a delay in tissue maturation, expanding immature cells, which in turn, decreases the number and the location of mature cells within the tissue. Hence, it can be considered the earliest form of pre-cancerous lesions. Therefore, high-grade dysplasia is synonymous with ‘carcinoma in situ’. Neoplasia is the condition in which the entire epithelium becomes dysplastic. 

Figure 2: Cancer Progression

Genetic alterations such as inactivation of tumor suppressor genes and activation of oncogenes are often a cause for dysplasia. Therefore, it can be reversible only by shedding off the diseased cells from the epithelium during its low-grade level. 

Similarities Between Metaplasia and Dysplasia 

• Metaplasia and dysplasia are two types of cellular changes that occur under the influence of various factors. 
• Both are abnormal changes in the nature of a tissue. 

Difference Between Metaplasia and Dysplasia 

Definition 

Metaplasia refers to the conversion of a mature, differentiated cell into another form of a mature cell type, often following injury or insult whereas dysplasia refers to the development of abnormal types of cells within a tissue, which may signify a stage preceding the development of cancer. 

Type of change 

That is, the metaplasia is the conversion in cell type while the dysplasia is the change in the phenotype of cells or a tissue. 

Occurs in 

Furthermore, Metaplasia occurs in various types of tissues while dysplasia mainly occurs in the epithelium. 

Causes 

Moreover, metaplasia is an adaptive process that occurs due to an external stimulus while dysplasia occurs due to the alteration of genetic material. 

Reversibility 

Also, the metaplasia is a reversible process while high-grade dysplasia is an irreversible process.  

Malignancy 

Importantly, metaplasia does not lead to the formation of cancers while dysplasia may cause cancers.  

Conclusion 

Metaplasia is the conversion of one form of differentiated cells into another form of differentiated cells in response to an external stimulus. On the other hand, dysplasia is an abnormal growth form of an epithelium, which can be pre-cancerous in its high-grade conditions. The main difference between metaplasia and dysplasia is the type of transformation. 

Reference:

1. Cheprasov, Artem. “Metaplasia: Definition, Symptoms & Examples.” Study.com, Study.com, Available Here
2. “Dysplasia : Cancer Glossary | CTCA.” CancerCenter.com, 1 Jan. 1AD, Available Here

Image Courtesy:

1. “Barretts esophagus alcian blue high mag” By Nephron – Own work (CC BY-SA 3.0) via  Commons Wikimedia 
2. “Cancer progression from NIH” (Public Domain) via Commons Wikimedia