Morphological Response of Respiratory Epithelium to Carcinogens, Syrian Hamster (Mesocricetus auratus W.)

Early morphological changes of the respiratory epithelium in the larynx, trachea, and stem bronchi that may lead to or are associated with the occurrence of neoplasia cannot be easily observed and diagnosed macroscopically. Exophytic papillary tumors, regardless of whether they fill the airway lumen, are detectable under a magnifying glass, a stereo microscope (Fig. 99), or even by the naked eye. In addition to their typical form and shape (sessile or pedunculated), the tumors are soft and reddish gray, clearly distinguishable from the surrounding normal respiratory epithelium. Small tumors are often indicated by focally increased vascularization at the site of origin. After perfusion of the tissues with fixative these neoplasms become a yellowish gray contrasting with the whitish adjacent epithelium. Macroscopically, invasive tumors and masses outside of the airways are usually found during necropsy, tissue trimming, and dissection.