03.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. Metaplasia is the exchange of normal epithelium for another type of epithelium. Metaplasia is reversible when the stimulus for it is taken away.

03.肿瘤形成的第一步是细胞转变，吸烟的慢性刺激导致喉部呼吸上皮的化生，一种上皮（右边的正常呼吸上皮）向另一种上皮（左边更富弹性的鳞状上皮）转变。当刺激因素消除后，化生可恢复。