A histological study of formation and growth of nasal polyps.

Chronic infection and allergy are considered to be the two major etiologic factors of nasal polyps. Whatever its cause may be, the initial phase of nasal polyp formation is represented by increased exudation from vessels, edema of the lamina propria and the bulging of the nasal mucosa. Nasal polyps were histologically classified into three types: edematous type, glandular and cystic type (ductal type) and fibrous type. Those of the edematous type and the glandular and cystic type are in the active stage of tissue reaction because of permeation of vascular fluid and marked infiltration of round cells. Contrastingly, the fibrous type polyps are in the healing stage of tissue reaction because of marked proliferation of fibroblasts and collagen fibers. The morphological structure of the nasal glands involved in the bulging mucosa determines the type of nasal polyps, whether edematous type or glandular and cystic type.