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The first step toward neoplasia is cellular transformation. The chronic irritation from cigarette smoke has led to an exchanging of one type of
epithelium (the normal respiratory epithelium at the right) for another (the more resilient squamous epithelium at the left). Thus, there is metaplasia of normal respiratory laryngeal epithelium to squamous epithelium 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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