P16INK4A as an adjunct test in liquid-based cytology

Anal Quant Cytol Histol. 2003 Feb;25(1):8-11.


Objective: To assess the utility of P16INK4A as an adjunct test in liquid-based cytology in cases with equivocal morphologic changes of high grade squamous intraepithelial lesion (HSIL).

Study design: P16INK4A immunoreactivity was investigated in residual ThinPrep material (Cytyc Corp., Boxborough, Massachusetts, U.S.A.) from 30 cases with equivocal diagnoses of HSIL that had corresponding follow-up biopsies. Two control ThinPrep cases were included: 1 HSIL with biopsy-confirmed cervical intraepithelial neoplasia (CIN) 3 and a negative specimen with a corresponding biopsy of squamous metaplasia. The expression of P16INK4A in ThinPrep specimens and corresponding biopsies was scored as previously described. A ThinPrep case was scored positive if it contained > 10 abnormal cells with nuclear and cytoplasmic immunocytochemical staining. Corresponding biopsies were scored as having negative, sporadic, focal or diffuse staining.

Results: The P16INK4A antibody assay was positive in 19 of 30 ThinPrep cases (63.3%). Seventeen of the 19 (89.4%) biopsies corresponding to the positively stained ThinPreps also were positive, with a score of at least focal positivity in the dysplastic regions (2 CIN 1, 4 CIN 2, 11 CIN 3; 2 lesions lost in the tissue recut). The assay was negative in 11 ThinPreps (36.6%) and 10 biopsies (33.3%) with tissue confirmation of chronic cervicitis (5), squamous metaplasia (2), CIN 1 (3) and 1 lesion lost in the tissue recut. Seventeen of 18 (94.4%) ThinPreps confirmed as high grade lesions upon biopsy showed P16INK4A positivity. The control HSIL case with a CIN 3 biopsy was diffusely positive for P16INK4A, and the control negative case with biopsy diagnosis of squamous metaplasia was negative. Nondysplastic squamous and metaplastic epithelium in 7 biopsies and nondysplastic squamous or metaplastic cells in ThinPrep cases were negative. Sporadic staining of bacteria, inflammatory cells and endocervical cells was noted.

Conclusion: ThinPrep cases in the equivocal cytologic category with the corresponding tissue biopsy assayed for P16INK4A expression showed that there was utility for this type of testing. A larger series comparing corresponding ThinPrep and tissue biopsies will be undertaken. The role of HPV infection in these cases will also be explored.

Publication types

  • Evaluation Study

MeSH terms

  • Biopsy
  • Cell Count
  • Cervical Intraepithelial Neoplasia / chemistry
  • Cervical Intraepithelial Neoplasia / classification
  • Cervical Intraepithelial Neoplasia / pathology*
  • Cyclin-Dependent Kinase Inhibitor p16 / analysis*
  • Female
  • Humans
  • Immunohistochemistry / methods
  • Uterine Cervical Neoplasms / chemistry
  • Uterine Cervical Neoplasms / pathology*
  • Vaginal Smears / methods*


  • Cyclin-Dependent Kinase Inhibitor p16