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 st udied for their histologic types, immunohistochemical features, and associa tion 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 conve ntional NPC were included for comparison. The prevalence rate of salivary g land type NPCs was 1.3% of the total NPCs in this series. The patients cons isted 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 unu sual psammomatous variant was found. Others were adenoid cystic carcinomas and various adenocarcinomas, including a papillary adenocarcinoma. A compos ite tumor of adenocarcinoma and undifferentiated carcinoma was also observe d. The tumors were positive for AE1 and CK19 and generally negative for AE3 and CK20. Most cases were positive for epithelial membrane antigen and CA1 9-9 with sporadic expression of carcinoembryonic antigen (CEA) and S-100 pr otein. Conventional NPC differed only in consistent immunonegativity for CA 19-9 and CEA. EBV was detected by EBER ISH in 9 of 15 cases (60%) and by PC R 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 c onferring 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 inf ormation already died of the disease with a median survival of only 1 year.