High p16 Antibody Levels May Signal HPV Infection in Head and Neck Cancer
By Caroline Helwick
Medscape Medical News
November 3, 2009 (Chicago, Illinois) — In patients with head and neck squamous cell carcinoma (HNSCC), high p16 antibody expression might serve as a marker for infection with high-risk human papillomavirus (HPV). If validated, it could serve as a cost-effective alternative to more expensive tests, University of Alabama researchers reported here at the American Society for Clinical Pathology 2009 Annual Meeting.
Recently, infection with high-risk serotypes of HPV has been linked to a subset of HNSCC. The preferred methods for detecting HPV in tissue section are in situ hybridization (ISH) and polymerase chain reaction (PCR).
The current study evaluated the benefit of combining immunohistochemistry (IHC) for HPV and p16, a known surrogate marker for HPV infection, as a more cost-effective alternative to ISH and PCR in detecting HPV, said lead author Elizabeth Kerr, MD, from the University of Alabama at Birmingham.
"In this study, 73% of HNSCC [patients] were positive for high-risk HPV," she reported. "HPV detection by IHC was negative in all our samples, but p16 (3+) strongly correlated with high-risk HPV."
Dr. Kerr's team searched the University of Alabama's database for oral and pharyngeal dysplasia and carcinoma cases between January 2008 and July 2009. They selected only cases in which HPV status was confirmed on PCR by an outside reference lab. The HPV test results were undisclosed to the examining pathologists.
The sample consisted of 16 patients (13 men, 3 women), with a median age of 50 years. Tissue was immunohistochemically stained with the p16 and HPV antibodies. Nuclear staining of squamous cells for p16 was considered negative (no staining or <10% of cells stained), 1+ (11% to 30% of cells stained), 2+ (31% to 50% of cells stained), or 3+ (>50% of cells stained). Nuclear staining of more than 10% of squamous cells was considered positive for HPV. Additionally, samples were tested in-house for HPV with an ISH assay using the HPV?III family probe.
The results of the HPV and p16 IHC testing correlated with those obtained with PCR and ISH.
In 9 of 16 lesions, p16 (3+) expression was detected. All lesions were squamous cell carcinoma — 8 were from the tonsils or oropharynx and 1 was from the nasopharynx. One of the squamous papillomas showed p16 (2+) staining, and another showed p16 (1+) staining. None of the lesions stained positive for HPV with IHC.
Eight lesions were positive for high-risk HPV according to in-house ISH. All were squamous cell carcinoma and arose in the tonsils or oropharynx. There was a strong correlation between p16 (3+) IHC and ISH-detected high-risk HPV, Dr. Kerr reported.
The same 8 lesions that were positive for ISH-detected high-risk HPV were positive for PCR-detected high-risk HPV. There were 4 squamous papillomas (from the larynx, glottis, and trachea) that were positive for PCR-detected low-risk HPV.
"Those cases of p16 (3+) by IHC correlated with high-risk HPV PCR and showed 100% sensitivity and 87.5% specificity," Dr. Kerr noted. The in-house ISH-detected high-risk HPV also correlated with PCR-detected high-risk HPV and showed 100% sensitivity and 100% specificity.
The authors concluded that because p16 (3+) cases strongly correlated with PCR-detected high-risk HPV and ISH-detected high-risk HPV, p16 could be used as a surrogate marker for HPV infection, and would be a cost-effective alternative to the more expensive PCR and ISH assays.
Isam A. Eltoum, MD, professor of pathology at the University of Alabama at Birmingham, who was not involved in this study, told Medscape Pathology that "this is a good preliminary study, especially because the reviewers were blinded, but it needs to be confirmed in a larger series."
"If p16 can be confirmed as a useful surrogate, this would be helpful to the pathologist because it is routine in what we do, unlike PCR, which must be done by a molecular lab," said Dr. Eltoum, who is an expert in HPV infections. "Here, the same pathologist could order the p16 and see immediately whether the lesion is HPV-related. It would all be in the hands of the pathologist."
Dr. Kerr and Dr. Eltoum have disclosed no relevant financial relationships.
American Society for Clinical Pathology (ASCP) 2009 Annual Meeting: Abstract 84. Presented October 30, 2009.
