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Dysplasia is a medical term formed from the Greek roots literally meaning 'bad' + 'formation'. This is a quite accurate translation in many cases, as it often has only a very imprecise meaning. For example, hip dysplasia is generally the same as saying "this hip has grown wonky". This leads to some confusing terminology, with some professionals preferring slightly more targeted terms like 'congenital dislocation of the hip' or 'hip instability'.

However, there are some more specific uses of the term with well-defined technical meanings. Most notably:

1. In oncology, dysplasia refers to the presence of abnormal cells within a tissue.

In many cases dysplasia is a precursor to cancer; in this case a distinction is made between dysplasia, in which cells are seen to be abnormal, and hyperplasia, in which there is an abnormal increase in the number of cells. (The term neoplasia -- or, if you are a normal person, tumor -- is used when the increase in cells is great enough to cause a visible or palpable lump). While we tend to associate cancer primarily with hyperplasia, a precancerous lesion would be a case of dysplasia.

2. In embryology and infant development, dysplasia refers to the abnormal development of tissue resulting from abnormal cell development or growth.

This is a common cause of developmental defects, although certainly not the only one. In dysplasia, large-scale body tissues -- e.g. muscles or bone -- do not develop properly due to abnormal cell development rather than due to abnormal morphogenesis or outside forces. Perhaps the most familiar type of developmental dysplasia is skeletal dysplasia (AKA dwarfism), in which abnormal cell growth in some portion of bone and/or cartilage results in a smaller body or shortened limbs.

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