Changes in Histological Features of Nasal Polyps in a Korean Population over a 17-year Period

Objective Nasal polyps can be categorized as eosinophilic or non-eosinophilic, depending on inflammatory cell infiltration. There are geographical differences in the prevalence of types of pathologic polyps. The aim of this study was to evaluate the change in the prevalence of histological subtypes of polyps over time in a Korean population. Study Design A retrospective cross-sectional study with histologic analysis. Setting A single academic medical center. Subjects and Methods A total of 230 patients with nasal polyps were enrolled between 1993-1994 (group A) and 2010-2011 (group B). Specimens were fixed in formalin and embedded into paraffin blocks. Slides were stained with hematoxylin-eosin (H&E) and were subsequently reviewed by 2 of the authors. The numbers of eosinophils per high power field (HPF), as well as other cellular, epithelial, and stromal markers, were recorded. Results We compared nasal polyp eosinophil counts according to time period. The average eosinophil count/HPF increased from 6.8 in group A to 19.3 in group B (P = .006). The prevalence of eosinophilic polyps also increased from 24.0% in group A to 50.9% in group B (P < .001). Among other histologic markers, lymphocytes, basement membrane thickening, and gland hyperplasia showed significant differences between groups. Conclusion After comparison of histopathologic findings of nasal polyps from 1993 and 2011 at 1 academic medical center in Korea, the prevalence of eosinophilic nasal polyps, which are known to be rare among Asians, has significantly increased.