Epstein-Barr virus-associated poorly differentiated nasopharyngeal adenocarcinoma: a case report and literature review.

Primary Epstein-Barr virus (EBV)-associated poorly differentiated nasopharyngeal adenocarcinoma (NAC) is an extremely rare tumor. In this study, we report a case of EBV-associated poorly differentiated NAC in a 35-year-old man who presented with a clogging sensation in the right ear for 1 month. The first biopsy of the nasopharynx was suggestive of nonkeratinizing carcinoma with weak positivity for CK5/6 and p63. Based on magnetic resonance imaging of the nasopharynx and neck, chest computed tomography, abdominal ultrasound, and whole-body bone scan, the patient was diagnosed with T3N2M0 disease. After the patient received neoadjuvant chemotherapy, concurrent chemoradiotherapy, and adjuvant chemotherapy, partial remission was observed. However, reassessment after 7 months of treatment revealed tumor enlargement. Transnasal endoscopic resection was performed to remove the nasopharyngeal tumor. The postoperative immunostaining results were as follows: CK5/6 (-), p63 (-), MOC31 (+), and Ber-EP4 (+). Meanwhile, EBV-encoded RNA in situ hybridization was positive. A final diagnosis of EBV-associated poorly differentiated NAC was made. Then, the patient received chemotherapy and irradiation but died several months later because of disease progression. Our patient presented with highly malignant EBV-associated poorly differentiated NAC insensitive to chemoradiotherapy with a short survival time of 27 months.