The presence of herpesviruses in malignant but not in benign or recurrent pleomorphic adenomas.

BACKGROUND: The etiology of salivary gland tumors is mainly unknown. The anatomical location of the salivary glands, with the mucosal pathway to the oral cavity and its rich microbiome, raises the question of potential viral background. OBJECTIVE: This study focuses on the potential presence of herpes-, polyoma- and parvoviruses in pleomorphic adenoma (PA), recurrent pleomorphic adenoma (RPA) and carcinoma ex pleomorphic adenoma (CaxPA). METHODS: Thirty different viruses were analyzed by PCR-based assays in 68 formalin-fixed paraffin-embedded salivary gland tumors (25 PA, 31 RPA and 12 CaxPA). RESULTS: Virus DNA was detected altogether in 19/68 (28%) tumor samples. Human herpesviruses 6B and 7 (HHV-6B and HHV-7) and Epstein-Barr virus (EBV) were frequently and almost exclusively found in CaxPA (5/12, 7/12, and 3/12, respectively). Within the 7 CaxPA that were virus-positive, 3 samples contained 3, and 1 sample even 4, different viruses. Infrequent viral positivity was shown for parvovirus B19 and cutavirus, as well as Merkel cell and Malawi polyomaviruses. CONCLUSIONS: Our unexpected finding of herpesvirus DNA almost exclusively in CaxPA tissues deserves further in-depth studies.

Increased MIB-1 expression in salivary gland pleomorphic adenoma that recurs and undergoes malignant transformation.

The objective of this retrospective study was to explore possible changes in histopathological features and expression of cyclin D1 and MIB-1 in salivary gland pleomorphic adenoma (PA) that recur or undergo malignant transformation. Knowledge of these characteristics might help to guide the management of these rare tumors. The histopathology and immunohistochemical staining characteristics of such tumors were analyzed in a cohort of 65 patients constituting three different groups of tumors: PA, recurrent pleomorphic adenoma (RPA) and carcinoma ex PA (CxPA). The RPAs were divided into two subgroups: primary PA that were known to recur later (PA-prim) and recurrent tumors appearing after a primary tumor (PA-rec). RPAs and CxPAs were compared with PAs without recurrence, which served as a control group. In our study, CxPA and PA-rec, but not PA-prim, showed increased MIB-1 expression compared with the control group. Neither cyclin D1 expression nor any histopathological features showed any association in statistical analyses. CxPA showed increased mitotic activity, squamous metaplasia, and nuclear atypia. Tumor multifocality was more frequent in PA-rec and CxPA. The different MIB-1 expression in CxPA and PA-rec in comparison to PA-prim suggests that the changes in expression could develop after the primary tumor.