Human papillomavirus and salivary gland neoplasia: a p16INK4 immunohistochemical and in situ hybridisation study

OBJECTIVE

This study aimed to evaluate the association between human papillomavirus infection and salivary gland tumours in a Scottish cohort.

METHODS

Specimens from a range of salivary gland tumours operated on between 1997 and 2012 were studied. A tissue microarray constructed from tissue blocks was subjected to p16INK4 (cyclin-dependent kinase inhibitor 2A) immunohistochemistry and in situ hybridisation using probes specific for human papillomavirus, including types 16 and 18.

RESULTS

A total of 61 tumours (benign and malignant) were deemed suitable for the study. p16INK4 staining yielded three (4.9 per cent) positive samples: one small cell carcinoma, one squamous cell carcinoma and one poorly differentiated carcinoma. Human papillomavirus in situ hybridisation demonstrated a positive signal in the latter sample only (1.6 per cent).

CONCLUSION

This study demonstrated a very low human papillomavirus detection rate in salivary gland tumours. It can therefore be concluded that human papillomavirus infection is unlikely to play a role in salivary gland neoplasia. Rare human papillomavirus positive cases should be carefully evaluated to exclude the possibility of a metastatic lesion.

Pleomorphic adenoma of the nasal septum and its relationship with Epstein-Barr virus

OBJECTIVES

Pleomorphic adenoma is the most common benign tumor of the major salivary glands, especially of the parotid gland. It is much less common in the minor salivary glands of the oral cavity, and it rarely occurs in others sites in the head and neck. Even if virus involvement in salivary glands tumor has been many times discuted, the etiology of this tumor keeps being unknown. As compared to other nasal tumors, we tried to prove if Epstein-Barr virus (EBV) could be involved in the development of pleomorphic adenoma in this particular nasal localization.

METHODS

Three cases of pleomorphic adenomas of the nasal septum (two women and a man in age of 23-59 years) were retrospectively studied. All had positive rate of EBV-related blood antibodies. All the patients had undergone endoscopic surgery to remove the complete tumor. We used hybridation technique in the search for EBV-DNA in the three tumors.

RESULTS AND CONCLUSION

We had positive EBV-DNA detection in the tumor in one case, which seemed to prove relationship between pleomorphic adenoma and this virus. The literature concerning the subject is reviewed in order to explain EBV involvement in the development of such tumors in this particular localization.

Low prevalence of transfusion transmitted virus (TTV)-like DNA sequences in cystadenolymphoma and pleomorphic adenoma of the salivary glands

Titers of transfusion transmitted virus (TTV)-like DNA in saliva samples have been reported 100-1,000 times higher than those of the corresponding sera, suggesting viral transmission by saliva droplets. The present study was conducted to determine whether TTV-like DNA sequence elements play a role in the pathogenesis of cystadenolymphoma or pleomorphic adenoma and if the parotid or the submandibular gland is a major source of TTV persistence. Sixty-two archival salivary gland samples (16 cystadenolymphomas, 13 pleomorphic adenomas, and 33 controls) and 23 corresponding saliva samples were examined using a polymerase chain reaction (PCR) for TTV DNA. All PCR products that displayed DNA bands were sequenced. Leder's stain and immunohistochemistry (anti-CD8, anti-CD20, anti-CD45R0, anti-CD68, and anti-Ki67/MiB1) were applied to detect possible changes associated with findings of TTV-like DNA sequences. Tissue displayed TTV-like DNA sequences in 8.1% (5/62; saliva: 47.8%, 11/23). Tissue that contained TTV-like DNA sequences was histologically indistinguishable from samples lacking such DNA. TTV appears to be only a bystander in cystadenolymphoma, pleomorphic adenoma, and other salivary gland affections. Neither of the glands seems to be a major source of TTV persistence.

Simian virus 40 sequences and expression of the viral large T antigen oncoprotein in human pleomorphic adenomas of parotid glands

Simian virus 40 (SV40) sequences of the early region coding for the large T antigen (Tag) oncoprotein were investigated in DNA samples from human pleomorphic adenoma (PA) of parotid glands. Specific SV40 sequences were detected, by PCR and filter hybridization with an internal oligoprobe, in 28 of 45 (62%) human PA specimens. None of the DNA samples from 11 normal salivary gland tissues was SV40-positive. DNA sequence analysis, carried out in all PCR amplified products from SV40-positive PA specimens, confirmed the SV40 specificity and indicated that PCR products had a sequence not distinguishable from SV40 DNA wild-type strain 776. SV40 Tag expression was revealed by immunohistochemistry with the specific monoclonal antibody Pab 101 in PA thin sections with a highly sensitive technical approach which retrieved the nuclear viral oncoprotein in 26 out of 28 (93%) samples previously found SV40-positive by PCR. Detection of SV40 sequences and Tag expression in human PA suggests that this oncogenic virus may play a role as a cofactor in the onset and/or progression of this benign neoplasm, or that SV40 DNA could replicate and express the Tag in PA cells.

Role of Epstein-Barr virus and cytomegalovirus in the etiology of benign parotid tumors

BACKGROUND

Pleomorphic adenomas and Warthin's tumors are the two most common benign parotid tumors. Previous studies investigating the role of viruses in tumorigenesis of these neoplasms have been conflicting. The aim of this study was to determine whether Epstein-Barr virus (EBV) or cytomegalovirus (CMV) might play a role in the pathogenesis of pleomorphic adenomas and Warthin's tumors.

METHODS

Paraffin-embedded surgical specimens of 24 pleomorphic adenomas, 10 Warthin's tumors, and 13 normal parotid tissues were obtained from the University of California-San Francisco Pathology Department. Genomic DNA was extracted from the specimens, and primers for connexin 26, a gap junction protein, were used to confirm the integrity of this DNA. The presence or absence of EBV and CMV DNA within the samples was determined with PCR-based assays, in which radiolabeled primers were used for maximal sensitivity of detection.

RESULTS

PCR analysis of serially diluted control DNA revealed that using radiolabeled primers, five copies of viral DNA could be detected. By use of this method, we showed that none of the 24 pleomorphic adenomas, 10 Warthin's tumors, or 13 normal parotid samples contained EBV DNA or CMV DNA.

CONCLUSIONS

These results do not support CMV or EBV as etiologic factors in pleomorphic adenomas or Warthin's tumors. In addition, normal parotid seems not to harbor either of these viruses. Future studies with larger numbers of specimens are needed to confirm these findings.

[Clinical study of bilateral parotid tumors]

We studied retrospectively 212 patients with parotid tumors who were treated in our hospital between October 1981 and March 1998. One hundred seventy-two of the tumors were benign, and 40 of them were malignant. The tumors were bilateral in 13 patients. Since 1992, we have treated at least 1 bilateral parotid tumor patient per year, and the number of patients with bilateral parotid tumors has tended to increase. Histologically, adenolymphomas occurred in 11 patients, and there was one occurrence of pleomorphic adenoma and one occurrence of basal cell adenoma. Eighty-five percent of all bilateral parotid tumors were adenolymphomas, and the bilateral parotid tumors comprised twenty percent (11 of 53 patients) of all adenolymphomas that we encountered. Among the 13 patients with bilateral parotid tumors, 1 patient experienced them heterochronously. In 7 of the 13 patients the tumor on the opposite side was found by diagnostic imaging. One patient showed recurrence in both parotid glands 4 years after initial surgery. Comparing bilareral adenolymphomas with unilateral adenolymphomas, there was no significant difference in the age or sex of the patients. Regarding bilateral adenolymphoma, 4 patients showed a solitary tumor on either side, 4 patients showed a solitary tumor on one side and multiple tumors on the other side, and 4 patients showed multiple bilateral tumors. Regarding unilateral adenolymphoma, 38 patients showed solitary tumors and 4 patients showed multiple tumors. Bilateral adenolymphomas were more multicentric than unilateral adenolymphomas. Epstein-Barr virus-encoded RNA (EBER) was detected in 11 of the 12 bilateral adenolymphomas and in 18 of 35 patients with unilateral adenolymphoma, by in situ hybridization. EBER was detected more frequently in the multiple unilateral adenolymphomas than in the solitary unilateral adenolymphomas. Based on our experience, the bilateral parotid tumor is not rare. Care should be taken to observe the other side of the parotid gland with parotid tumors that are suspected adenolymphomas. Imaging may be helpful for the detection of bilateral tumors. A relationship may exist between Epstein-Barr virus and adenolymphoma multicentricity.