Clinical and Histopathological Classification of Nasal Polyps in Thais

One hundred and forty five patients with nasal polyps (NP) who underwent a first operation at the Department of Otolaryngology, Faculty of Medicine Siriraj Hospital during the 2-year period January 1998 to December 1999, were studied to determine the incidence of clinical and histolopathologic types of NP in Thai patients. The clinical types of NP were classified into 5 groups, using Stammberger's criteria i.e. isolated polyps (IP); antrochoanal polyps (ACP); NP and chronic rhinosinusitis (NPCRS) associated with non-eosinophilic infiltration; NPCRS associated with eosinophilic infiltration or NP with asthma (NPA); and NP with specific diseases (NPSD). The histopathologic types were classified into 4 types, using Hellquist's criteria i.e. Type I, edematous, eosinophilic (allergic) polyps; Type II, chronic inflammatory (fibroinflammatory) polyps; Type III, polyps with hyperplasia of seromucinous glands; and Type IV, polyps with stromal atypia.    There were 86 males (59.3%) and 59 females (40.7%), with a male : female ratio = 1.5 : 1. The mean age was 36.1 ± 16.5 years, ranging from 9 to 74 years. The mean duration of symptoms was 63.6 ± 75.2 months, ranging from 1-420 months. The clinical classification study showed that 17 patients (11.7%) had IP, 13 patients (8.9%) had ACP, 105 patients (72.4%) had NPCRS, 5 patients (3.5%) had NPA, and 5 patients (3.5%) had NPSD (one case of Katargener's syndrome, bronchiectasis, aspirin intolerance, immotile cilia syndrome, and AIDS respectively). The histopathologic study showed that 17 specimens (11.7%) were Type I, 118 specimens (81.4%) were Type II, 9 specimens (6.2%) were Type III, and 1 specimen (0.7%) was Type IV.    In the group of patients with NPCRS (105 patients), the most common histopathologic type was type II (86 patients, 81.9%). Type I and Type III were found in 12 patients (11.4%) and 7 patients (6.7%) respectively. The incidence of eosinophilic polyps in the groups of NPCRS was only 18.1% (Type I + Type III). This finding is different from that of NP in the western countries, in which the incidence of eosinophilic polyps is 80-90%. The pathogenetic mechanism underlying this difference is still not known. Is this difference due to racial or genetic factors, or geographic differences? The answers to these question are to be studied further