Pathogenesis and Etiology of Nasopharyngeal 2 Carcinoma

Nasopharyngeal carcinoma (NPC) is a squamous cell carcinoma (SCC) that usually develops around the ostium of the Eustachian tube in the lateral wall of the nasopharynx (Sham et al. 1990). This disease was initially reported in 1901 and characterized clinically in 1922 (Wei et al. 2005). NPC is a disease with a remarkable geographic and racial distribution worldwide. This is a rare human malignancy with an incidence below 1/100,000 populations per year in Caucasians from North America and other Western countries. In contrast, the highest incidence is noted in the Southern Chinese population of Guangdong, Inuits of Alaska, and native Greenlanders (Chou et al. 2008; Parkin et al. 1992); particularly, among the Cantonese who inhabit the central region of Guangdong Province in Southern China, the incidence is 15–25 cases per 100,000. NPC is also called the “Canton tumor” in Guangdong Province (Hepeng 2008; Yu et al. 2002). Southern Chinese migrants, irrespective of their country of migration, also exhibit high rates of NPC (Yu et al. 2002), but the rate of NPC among ethnic Chinese born in North America is considerably lower than those born in China (Buell 1974). An intermediate incidence has been reported in Alaskan Eskimos and in the Mediterranean basin (North Africa, Southern Italy, Greece, and Turkey), ranging from 15 to 20 cases per 100,000 persons (Chan et al. 2002). Independence of race– ethnicity, the rates of NPC in men are two to three folds higher than those in women for most populations (Yu et al. 2002). Overall, NPC can occur in all age groups, but has a bimodal age distribution. The incidence peaks at 50–60 years of age, and a small peak is observed during late childhood (Jeyakumar et al. 2006). The distinct difference in the incidence among geographic and population area implies that both Pathogenesis and Etiology of Nasopharyngeal 2