The prognostic value of histological typing in nasopharyngeal carcinoma

We analyzed the relation of histological typing in late stage nasopharyngeal carcinoma (NPC) with clinical outcome and excision repair cross complementation group 1 protein (ERCC1) expression. The biopsy specimens of 259 patients with NPC were reviewed by two pathologists for classification according to 2005 WHO subtypes. The patients were of stage III to IVB and treated with radiotherapy (RT) alone or concurrent-adjuvant chemoradiotherapy (CRT). Expression of ERCC1 protein detected by immunohistochemistry on paraffin sections was correlated with the histological subtypes. There were 10 cases (3.9%) of differentiated non-keratinizing carcinoma compared with 249 cases of conventional undifferentiated carcinoma. The former exhibited more advanced squamous differentiation with 3 cases belonging to the papillary variant. The degree of ERCC1 expression was generally high compared with the median of the cohort. Clinically, the differentiated group fared poorly compared with the undifferentiated group with respect to loco-regional failure-free rate, distant failure-free rate, disease-free survival and overall survival (p≤0.05). Treatment modality of the 10 patients (5 RT, 5 CRT) was similar to the whole cohort. Contrary to general acceptance that differentiation of non-keratinizing NPC had little bearing on prognosis, we demonstrated that in endemic area differentiation in fact conferred a worse prognosis in stage III to IVB patients. There was positive correlation of differentiation with ERCC1 expression. We advocate precise histological typing of NPC in pathology report for prognostic purpose and outcome correlation.