EBER1 in situ hybridization as an adjuvant for diagnosis of recurrent nasopharyngeal carcinoma.

The mainstay treatment of nasopharyngeal carcinoma (NPC) is radiotherapy. Although NPC is a radiosensitive tumor, 25% of NPC patients still suffered from local relapse in Taiwan. Whether the pathologic changes induced by radiation have impact on the interpretation of suspicious recurrent NPC specimens is seldom mentioned. We retrospectively analyzed 20 irradiated NPC patients who were suspected to have local recurrence and received serial nasopharyngeal biopsies. A total of 31 nasopharyngeal tissues including 15 local recurrent specimens and 16 negative specimens were entered into this study. Compared with non-irradiated nasopharyngeal tissue, the irradiated nasopharynx showed fibrosis and areas of necrosis mixed with acute or chronic inflammation. Stroma cells were enlarged, with prominent nuclei and cytoplasm, and some bizarre cells might be confused with tumor cells. These post-irradiation effects did have an impact on histological interpretation. In this study, 2 out of 16 nasopharyngeal tissues were misdiagnosed as having no recurrent tumor by using H and E stain only. However, scattered cancer cells can be clearly visualized by using EBER1 in situ hybridization. Therefore, it is recommended that EBER1 in situ hybridization is routinely used in irradiated nasopharyngeal tissues in helping the diagnosis of recurrent NPC.