The Diagnostic Utility of Cell Blocks Prepared From Residual SurePath Pap Material for Detection of Human Papilloma Virus

Abstract

This study was undertaken to determine if tissue sections from cell block prepared from the residual cellular sediment of Pap test vials could be used for immunohistochemistry (IHC) or in situ hybridization (ISH) for the detection of human papilloma virus (HPV) and to determine if these stains could clarify the nature of atypical cases in certain cases. Cases included in this retrospective study are categorized into 3 groups. Group 1 included 12 positive and 10 negative cases that were used to optimize the IHC and ISH staining protocol for the detection of HPV. Cases selected in group 2 were included to validate and verify the IHC and ISH stains. We validated 20 negative and 37 positive cases. Group 3 included 37 atypical cases. Unused material from the corresponding liquid-based (SurePath) Pap test specimens were retrieved and used to prepare paraffin-embedded cell blocks. Hematoxylin and eosin-stained cell-block sections were evaluated for abnormal cells. The IHC and ISH stain protocols for detection of HPV DNA were successfully optimized, validated, and verified. The sensitivity for the detection of HPV DNA using IHC in atypical squamous cells of undetermined significance was 80% and in atypical squamous cell, cannot rule out high grade, was 78% whereas the specificity was 100% in both lesions. Both the sensitivity and specificity for the detection of HPV DNA using the ISH were 100%. This study demonstrated that cell-block sections prepared from residual SurePath Pap test material could be used for detection of HPV DNA by both IHC and ISH and clarify the nature of atypical cells on cell-block sections.