Pathology of nasopharyngeal carcinoma. Proposal of a new histologic classification correlated with prognosis.

To establish a new histologic classification with better correlation with patient prognosis, the histologic features of nasopharyngeal carcinoma (NPC) were correlated with prognosis and clinical stage among 494 patients who had been followed a minimum of 5 years after initial radiotherapy. A slight modification of World Health Organization (WHO) classification by the separation of spindle cell variant from the nonkeratinizing (NK) and undifferentiated carcinomas (UD) provided a better prognostic correlation: keratinizing squamous cell carcinoma (KS), spindle cell carcinoma (SP), round cell carcinoma (RC), and mixed cell carcinoma (Mix, or NK); 5-year survival rates were 21%, 41%, 51.8%, and 54%, respectively. This prognostic distinction was further improved by dividing the three nonkeratinizing carcinomas (SP, RC, and Mix) into two subtypes each, according to the degree of cell anaplasia and pleomorphism: Type A (with marked anaplasia and/or pleomorphism), and Type B (with moderate or little anaplasia). The three Type A carcinomas had very similar 5-year survival rates (33.3 to 38.6%), as did the three Type B carcinomas (60% to 71.8%). Therefore, a working formulation for the malignancy of NPC emerged: high-grade malignancy (KS; 5-year survival, 21%), intermediate malignancy (Type A carcinomas, 5-year survival, 30%-40%), and low-grade malignancy (Type B carcinomas, 5-year survival rate, 60%-72%). The prognostic distinction remained true after stratification by clinical stage. Therefore, the histologic condition of the tumor of NPC correlated with patient's prognosis.