Dysplasia

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This article covers Dysplasia, a pre-cancerous change in cellular structures. For details on Hip dysplasia, a clinical condition affecting the hip joint (especially in dogs), please see the article on Hip dysplasia.

Dysplasia (from 'bad form', in Greek) is an abnormality in the appearance of cells indicative of an early step towards transformation into a neoplasia. It is therefore a pre-neoplastic change. This abnormal growth is restricted to the originating system or location, for example, a dysplasia in the epithelial layer will not invade into the deeper tissue, or a dysplasia solely in a red blood cell line (refractory anaemia) will stay within the bone marrow and cardiovascular systems. Though epithelial dysplasia may regress spontaneously, persistent lesions must be removed, either with surgery, chemical burning, heat burning, burning with laser, or freezing (cryotherapy).

The best known form of dysplasia is the precursor lesions to cervical cancer, called cervical intraepithelial neoplasia (CIN). This lesion is usually caused by an infection with the human papilloma virus (HPV). Dysplasia of the cervix is almost always unsuspected by the woman. It is usually discovered by a screening test, the pap smear. The purpose of this test is to diagnose the disease early, while it is still in the dysplasia phase and easy to cure.

[edit] Dysplasia vs carcinoma in situ vs invasive carcinoma

These terms are related since they represent the three steps of the progression towards cancer:

Dysplasia is the earliest form of pre-cancerous lesion recognizable in a pap smear or in a biopsy by a pathologist in which a cell begins to change away from its normal form to an abnormal, less differentiated form. Dysplasia can be low grade or high grade (see CIS below). The risk of low grade dysplasia transforming into high grade dysplasia and, eventually, cancer is low. Treatment is usually easy. High grade dysplasia represents a more advanced progression away from normal and nearing cancer transformation. Treatment is still easy at this stage.
Carcinoma in situ , meaning 'cancer in place', represents a final transformation of a dysplastic cell to cancer, though the cancer remains local and has not moved out of the original site. Cancer is a state where the cells have lost their tissue identity and have reverted back to a primitive cell form that grows rapidly and without regulation.
Invasive carcinoma is the final step in this sequence. It is a cancer which has invaded beyond the original tissue layer and is also able to spread to other parts of the body (metastasize), starting growth of the cancer there and destroying the affected organs. It can be treated, but not always successfully. However, if left untreated it is almost always fatal.

Metaplasia is a situation where cells have changed from their original mature differentiated type into another mature differentiated cell type as an adaptive response to exposure to chronic irritation, or to a pathogen or carcinogen. It also occurs where one normal cell type changes into another normal cell type as in the cervix where squamous epithelium on the exo-cervix changes to normal columnar epithelium in the endo-cervix. This area is also known as the transformation zone and is the location of many dyplastic lesions thus the sampling of this area during a pap test is critical. Metaplasia is distinct from dysplasia because in a dysplastic cell these changes have become encoded into the genome and so are heritable or passed on to daughter cells during cell replication.