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The first step toward neoplasia is cellular transformation. Here, there
is metaplasia of normal respiratory laryngeal epithelium on the right to
squamous epithelium on the left in response to chronic irritation of
smoking.
The two forms of cellular transformation that are potentially reversible, but may be steps toward a neoplasm, are:
Metaplasia: the exchange of normal epithelium for another type of epithelium. Metaplasia is reversible when the stimulus for it is
taken away.
Dysplasia: a disordered growth and maturation of an epithelium, which is still reversible if the factors driving it are eliminated.
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