HISTOPATHOLOGY

Sinonasal polyps are benign mucosal swellings that occur in four diffe rent histological patterns. The most common type is the edematous, eos inophilic (so-called ''allergic'') nasal polyp, which constitutes 85-9 0% of nasal nasal polyps. The edematous polyp is morphologically chara cterized by edema, goblet cell hyperplasia of the epithelium, thickeni ng of the basement membrane, and of numerous leukocytes, predominantly eosinophils. The second histological type is a fibroinflammatory poly p characterized by chronic inflammation and metaplastic changes of the overlying epithelium. Another rare variant presents with pronounced h yperplasia of seromucinous glands, but otherwise shows many similar it ies with the edematous type of polyp. The fourth type is very I are an d is a polyp with atypical stroma. This latter polyp calls for awarene ss and careful histological examination to avoid misdiagnosis of a neo plasm.