Determination of nonendemic nasopharyngeal carcinoma by in situ hybridization for Epstein-Barr virus EBER1 RNA: sensitivity and specificity in cervical node metastases.

After time-consuming and costly investigations, patients with neck metastases from an occult primary often receive unnecessarily large radiation volumes to treat a possible origin in the nasopharynx. In this study a colorimetric antisense Epstein-Barr early ribonucleoprotein 1 (EBER1) oligonucleotide probe specific for Epstein-Barr virus RNA was hybridized in situ to metastatic tissue obtained from 18 nasopharyngeal, 54 oral and pharyngeal, and 12 occult carcinomas derived from an unselected population. All 16 nonkeratinizing nasopharyngeal carcinomas (NPCs) were positive for EBER1. Both cases of keratinizing NPC and all 54 other metastases were negative. A single positive case of occult carcinoma indicated its origin from NPC. In retrospect, 7 patients with occult carcinoma had received unnecessary treatment with irradiation to the nasopharynx. Nasopharyngeal carcinoma appears to be a less common origin of occult carcinoma than previously considered. In the proper clinicopathologic context EBER1 in situ hybridization (EBER1-ISH) allows exclusion of NPC with a high degree of accuracy. Thus unnecessarily large radiation volumes and their adverse sequelae may be reduced in the treatment of occult carcinoma. Conversely, a positive result of ISH allows exclusion of further extensive diagnostic procedures.