Nasopharyngeal carcinoma: epidemiology, histopathology and aetiology.

The highest incidence of nasopharyngeal carcinoma (around 20 per 100,000 per year) is found in Chinese populations in many countries. Elevated rates (5--15) are found in Eskimos, and in several racial groups in South-East Asia. The incidence rates in Malta and in some parts of Northern Africa are also moderately elevated. The incidence rates are low (less than 1) in virtually all other parts of the world. In Singapore, the incidence rates are high in Chinese (18.4), intermediate in Malays (4.7) and low in Indians (less than 1). Among the various Chinese communities, the incidence rates in Cantonese (29.1 and 11.0 for males and females respectively) are significantly higher than those in Hokkiens (14.1 and 4.7), Teochews (18.3 and 6.2), Hainanese (14.2 and 3.3) and Hakkas (12.6 and 4.8). The tumour has a male preponderance (2--3 times) and a peak incidence in the 5th and 6th decades. Nasopharyngeal carcinoma (NPC) is the commonest form of nasopharyngeal cancer in man. All histological types of NPC have consistently shown ultrastructural evidence of squamous differentiation and may be regarded as variants of a homogeneous group of tumours. The development of the neoplasm is attributable to the action of environmental factors in genetically susceptible persons. There is growing evidence that nitrosamine compounds and the Epstein-Barr virus may be involved in the aetiology of this neoplasm.