MicroRNAs: novel factors in clinical diagnosis and prognosis for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a non-lymphomatous, squamous cell malignancy arising from the epithelial cells lining of the nasopharynx. Histologically, NPC has been classified into 3 types: keratinizing squamous cell carcinoma (WHO type I), differentiated non-keratinizing squamous cell carcinoma (WHO type II) and undifferentiated carcinomas (WHO type III). Compared to other malignant tumours of the upper aero digestive tract, NPC is a special type of head and neck cancer in terms of epidemiology, pathology and clinical presentation. The etiology of NPC involves multiple factors, including genetic susceptibility, exposure to chemical carcinogens and Epstein-Barr virus (EBV) infection^{1In some regions, notably the southern parts of China, and parts of Southeast Asia, this cancer occurs in an endemic form with an incidence 10- to 30-fold higher than in the other regions and, histologically, usually belongs to WHO type II and III. In the west, however, NPC occurs sporadically and usually belongs to WHO type I. There is also increased incidence in northern Africa and the Inuit of Alaska2,3}