Oronasopharyngeal and Salivary Gland Tumors Clinical and Morphological Investigation, the Role of the Herpes Group Viruses in the Malignant Process. Summary of the Doctoral Thesis

Abstract

The incidence of the oronasopharyngeal cancers increases in recent decades in Latvia. The tumors of the oronasopharyngeal region and salivary gland tumors represent the morphological diversity and different pathogenic pathways. The aim of the study was to investigate the clinical course and etiopathogenesis of the oronasopharyngeal and salivary gland tumors using clinical, morphological and molecular virusology methods; deciphering possible connection of herpes virus infection with these neoplasms. In this retrospective study 322 patients with the histologically confirmed diagnosis of salivary gland tumor treated between 1996 and 2007 at the Riga East University Hospital Oncology Center of Latvia in Department of Head and Neck Surgery were used. In total 212 female and 110 male patients were recorded. 32 parapharyngeal space tumors removed during surgeries as well as associated biopsies performed from 2001 till 2006 were also included in this study. Additionally one more group of patient consisted of 14 adult subjects with oral SCC and NPC attending the Oncology Center of Latvia between 2009 and 2011, were also eligible for the study, in this group EBV antibody titres and herpes viruses DNA was investigated. The present study showed that benign salivary gland tumors in the Latvian population are characterized by the incidence that is comparable with that in the other European populations; moderate tendency for female predominance. The appearance and elevation of stromal cell proliferative activity in the recurrent salivary gland pleomorphic adenoma may be responsible for more aggressive clinical behavior. EBV infection is a neoplasm co-morbid pathology which occurs in all common oronasopharyngeal tumors and is evidenced by elevated titers of antibodies. CD44, a cell surface receptor on the malignant oropharyngeal epithelial cells, lymphocytes and stromal macrophages in sustained EBV infection in patients with SCC and NPC suggests the CD44-mediated signaling in EBV infection and pathogenesis of oral and pharyngeal tumors. Identification of LMP1 expression and EBV DNA at advanced tumor stage (III, IV) should be taken into consideration. The herpes virus co-infection seems to play a significant role in pathogenesis of oral cancer.