[1930] Does p16 Immunostain Discriminate between Low-Risk and High-Risk Human Papilloma Virus Infection?

Thad M Primeaux, Jaiyeola Thomas. LSUHSC-Shreveport, LA

Background: p16, a cyclin-dependent kinase inhibitor and G1/S-phase cell cycle checkpoint regulator is often used as a marker of HPV and is an E7-mediated functional inactivator of retinoblastoma protein (pRB). The loss of pRB function leads to over-expression of p16 protein due to lack of negative feedback. E7 protein from HR-HPV is considered more effective in the inactivation of pRB compared to that of LR-HPV, hence the use of p16 as a surrogate marker of HR-HPV. This study aims to assess the efficacy of p16 staining to discriminate between HR-HPV and LR-HPV.
Design: 47 consecutive tissue biopies with HPV-ISH studies done within the last year were reviewed. All had 5-μm sections cut and stained with p16 antibody. p16 staining intensity and patterns were scored semi-quantitatively and correlated with the HPV-ISH results.
Results: Table 1 shows the HPV-ISH status and p16 staining correlation with tumor types. The LR-HPV HNSCC case was also HR-HPV+. Two laryngeal papillomas (LP), in addition to positive staining for LR-HPV, had focal HR-HPV positivity. The LP showed weak basal layer, membranous and scattered isolated p16+ epithelial cells, which was distinct from the full-thickness, intense, diffuse cytoplasmic and nuclear staining in HR-HPV+ tumors (Figures 1&2).

Table 1
Diagnosis# of casesLR-HPV DNAHR-HPV DNAp16Incomplete Data
Laryngeal papilloma642 (focal)4 (focal)0
Anal SCC30330
Perianal condyloma11100

Conclusions: HR-HPV+ tumors show full-thickness, diffuse strong positive nuclear and cytoplasmic staining of cell clusters. Reactive LR-HPV tumors show only focal weak basal layer staining and scattered single cell positivity. Therefore, p16 IHC can distinguish between LR-HPV and HR-HPV infection in tumors with intense, diffuse staining pattern seen in HR-HPV+. These patterns must be taken into consideration when interpreting positivity to effectively distinguish between LR-HPV and HR-HPV infection.
Category: Techniques

Monday, February 28, 2011 1:00 PM

Poster Session II # 257, Monday Afternoon


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