Histopathology of nasopharyngeal carcinoma: correlations with epidemiology, survival rates and other biological characteristics.

A total of 363 cases of nasopharyngeal carcinoma (NPC) in Singapore were classified into squamous cell carcinoma (SCC; 73 cases), non-keratinizing carcinoma (NKC; 178 cases) and undifferentiated carcinoma (UC; 172 cases). Possible biological differences between these histologic types and between tumors with and without lymphocytic infiltration were investigated by correlations with survival rates and with selected epidemiologic, immunovirologic, and immunogenetic data on the disease. The 5-year survival rates following radiotherapy were 25.3% for all cases and 58.8% for tumors restricted to the nasopharynx. The 5-year survival rate for SCC was poorer than for the combined NKC and UC groups (p less than 0.05). The 3-year survival rate was better for tumors with lymphocytic infiltration (p less than 0.05), but there were no differences in the 5-year survivals. The survival rates were better in females (p less than 0.01) and in the younger age groups (p less than 0.01). There were no significant correlations between histopathology of NPC and the distributions of cases by age, sex, HLA antigen profiles, or cell-mediated immune status. Squamous cell carcinoma was associated with lower levels of antibodies to the Epstein-Barr nuclear antigen (p less than 0.05), but there were no differences with respect to antibodies against other EBV related antigens. These findings support the view that SCC, NKC, and UC of the nasopharynx, as defined in the WHO classification, are variants of a fairly homogeneous group of neoplasms in the Singapore population.