Comparative Aspects of Pulmonary Carcinogenesis

Tumor classification systems are generally established to give the physician, scientist, toxicologist, or regulatory agency a means of relating to findings in a given patient, experiment, or toxicological study. Classification systems reflect the occurrence of lesions and the knowledge of a process regarding morphology and biological behavior (Table 9). A classification system based solely on histogenesis (McDowell et al. 1978; Becci et al. 1978) may be impossible to achieve, but several instances could allow for classifications according to cell types involved in both animals and humans.