Salivary gland type nasopharyngeal carcinoma - A histologic, immunohistochemical, and Epstein-Barr virus study of 15 cases including a psammomatous mucoepidermoid carcinoma

Salivary gland type nasopharyngeal carcinomas (NPCs) are rare and not well characterized. Fifteen NPCs with adenocarcinomatous differentiation were studied for their histologic types, immunohistochemical features, and association with Epstein-Barr virus (EBV) by EBER in-situ hybridization (ISH) and by polymerase chain reaction (PCR) to detect latent membrane protein-1 (LMP-1) gene with formalin-fixed, paraffin-embedded tissues. Two cases of conventional NPC were included for comparison. The prevalence rate of salivary gland type NPCs was 1.3% of the total NPCs in this series. The patients consisted of 11 men and 4 women with ages ranging from 15 to 74 years (median, 50 yrs). Mucoepidermoid carcinoma was the most common type (53%) and an unusual psammomatous variant was found. Others were adenoid cystic carcinomas and various adenocarcinomas, including a papillary adenocarcinoma. A composite tumor of adenocarcinoma and undifferentiated carcinoma was also observed. The tumors were positive for AE1 and CK19 and generally negative for AE3 and CK20. Most cases were positive for epithelial membrane antigen and CA19-9 with sporadic expression of carcinoembryonic antigen (CEA) and S-100 protein. Conventional NPC differed only in consistent immunonegativity for CA19-9 and CEA. EBV was detected by EBER ISH in 9 of 15 cases (60%) and by PCR of the LMP-1 gene in 10 of 15 cases (67%). Six of 10 LMP-I gene-positive cases (60%) had a specific deletion of 30-base pairs (bp) of the LMP-1 gene. The result also supports the possible importance of a 30-bp deletion in conferring the oncogenecity of the LMP-1 gene. The prognosis of this series of salivary gland type NPCs was poor. Six of 13 patients with follow-up information already died of the disease with a median survival of only 1 year.