Dysplasia is a term used in pathology

Pathology

Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

 to refer to an abnormality of development. This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells. Dysplasia is often indicative of an early neoplastic

Neoplasia

Neoplasm is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. The growth of neoplastic cells exceeds and is not coordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the...

 process. The term dysplasia is typically used when the cellular abnormality is restricted to the originating tissue, as in the case of an early, in-situ neoplasm.

Dysplasia, in which cell maturation and differentiation are delayed, can be contrasted with metaplasia

Metaplasia

Metaplasia is the reversible replacement of one differentiated cell type with another mature differentiated cell type. The change from one type of cell to another may generally be a part of normal maturation process or caused by some sort of abnormal stimulus...

, in which cells of one mature, differentiated

Cellular differentiation

In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...

 type are replaced by cells of another mature, differentiated type.

The terms hip dysplasia

Hip dysplasia

Hip dysplasia is an abnormal formation of the hip socket that, in its more severe form, can eventually cause crippling lameness and painful arthritis of the joints. It is a genetic trait that is affected by environmental factors...

 and fibrous dysplasia

Fibrous dysplasia

Fibrous dysplasia is a disease that causes bone thinning and growths or lesions in one or more bones, and leads to bone weakness and scar formation within the bones.-Presentation:...

 also refer to abnormal development, but at a more macroscopic level.

Examples

For example, epithelial dysplasia

Epithelial dysplasia

Epithelial dysplasia is the sum of various disturbances of epithelial proliferation and differentiation as seen microscopically. Individual cellular features of dysplasia are called epithelial atypia.The changes that occur in epithelial dysplasia include:...

 of the cervix (cervical intraepithelial neoplasia

Cervical intraepithelial neoplasia

Cervical intraepithelial neoplasia , also known as cervical dysplasia and cervical interstitial neoplasia, is the potentially premalignant transformation and abnormal growth of squamous cells on the surface of the cervix. CIN is not cancer, and is usually curable...

 – a disorder commonly detected by an abnormal pap smear

Pap smear

The Papanicolaou test is a screening test used in to detect pre-cancerous and cancerous processes in the endocervical canal of the female reproductive system. Changes can be treated, thus preventing cervical cancer...

) consists of an increased population of immature (basal-like) cells which are restricted to the mucosal surface, and have not invaded through the basement membrane

Basement membrane

The basement membrane is a thin sheet of fibers that underlies the epithelium, which lines the cavities and surfaces of organs including skin, or the endothelium, which lines the interior surface of blood vessels.- Composition :...

 to the deeper soft tissues. Analogous conditions include vaginal intraepithelial neoplasia

Vaginal intraepithelial neoplasia

Vaginal intraepithelial neoplasia is a condition that describes premalignant histological findings in the vagina characterized by dysplastic changes.The disorder is rare and generally has no symptoms...

 and vulvar intraepithelial neoplasia

Vulvar intraepithelial neoplasia

The term Vulvar intraepithelial neoplasia refers to particular changes that can occur in the skin that covers the vulva. VIN is not cancer, and in some women it disappears without treatment...

.

Myelodysplastic syndrome

Myelodysplastic syndrome

The myelodysplastic syndromes are a diverse collection of hematological medical conditions that involve ineffective production of the myeloid class of blood cells....

s, or dysplasia of blood-forming cells, show increased numbers of immature cells in the bone marrow

Bone marrow

Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

, and a decrease in mature, functional cells in the blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

.

Microscopic changes

Dysplasia is characterised by four major pathological microscopic changes:

1. Anisocytosis (cells of unequal size)
2. Poikilocytosis (abnormally shaped cells)
3. Hyperchromatism
4. Presence of mitotic figures (an unusual number of cells which are currently dividing).

Dysplasia vs. carcinoma in situ vs. invasive carcinoma

These terms are related since they represent the three steps in the progression of many malignant neoplasms (cancers)

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 of epithelial tissues

Epithelium

Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

. The likelihood of developing carcinoma is related to the degree of dysplasia.

• Dysplasia is the earliest form of pre-cancerous lesion which pathologist
  Pathology
  Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
  
  s can recognize in a pap smear or in a biopsy
  Biopsy
  A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
  
  . Dysplasia can be low grade or high grade (see "Carcinoma in situ," below). The risk of low grade dysplasia transforming into high grade dysplasia, and eventually cancer, is low. Treatment is usually straightforward. High grade dysplasia represents a more advanced progression towards malignant transformation.
• Carcinoma in situ
  Carcinoma in situ
  Carcinoma in situ is an early form of cancer that is defined by the absence of invasion of tumor cells into the surrounding tissue, usually before penetration through the basement membrane. In other words, the neoplastic cells proliferate in their normal habitat, hence the name "in situ"...
  
  , meaning "cancer in place", represents the transformation of a neoplastic lesion to one in which cells undergo essentially no maturation, and thus may be considered cancer-like
  Cancer
  Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
  
  . In this state, epithelial cells have lost their tissue identity and have reverted back to a primitive cell form that grows rapidly and with abnormal regulation for the tissue type. However, this form of cancer remains localized, and has not invaded past the basement membrane into tissues below the surface.
• Invasive carcinoma
  Carcinoma
  Carcinoma is the medical term for the most common type of cancer occurring in humans. Put simply, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that generally arises from cells originating in the endodermal or ectodermal germ layer during...
  
   is the final step in this sequence. It is a cancer which has invaded beyond the basement membrane and has potential to metastasize (spread to other parts of the body). Invasive carcinoma can usually be treated, but not always successfully. However, if it is left untreated, it is almost always fatal.