Expression of p16INK4A in Pap smears containing atypical glandular cells from the uterine cervix.
OBJECTIVE
To verify one of the diagnostic dilemmas concerning atypical glandular cells (AGC) by immunocytochemical detection of p16INK4A (p16) applied to routine Pap smears with correlation of follow-up biopsies for improvement of cytologic diagnoses.


METHODS
The study included 36 Pap smears in AGC diagnostic categories, all of which were correlated histologically. The cytologic diagnoses of AGC were further classified according to the 2001 Bethesda System. All Pap smears were decolorized and immunostained with the primary anti-p16 antibody, clone E6H4. Immunoreactivity for p16 was correlated with histologic sections in a semiblind fashion.


RESULTS
Of the 36 smears containing AGC, 22 (61%) were reclassified as general AGC and 14 (39%) as AGC--favor neoplasia. Follow-up biopsies revealed that 15 (42%) cervixes had no obvious abnormalities and that 21 (58%) cases had different cervical lesions. More than half the cases (19/36, 53%) of follow-up biopsies concerning AGC-containing smears represented significant lesions. There was a much higher proportion of significant lesions (13/14, 93%) in AGC--favor neoplasia than those (6/22, 27%) in general AGC cases. Fifteen of 36 (36%) AGC-containing cases were actually squamous abnormalities on follow-up biopsies. p16 Immunocytochemical stain was reactive in 22 (61%) of 36 smears, either weakly/sporadically (2 cases, 6%) or strongly positively (20 cases, 55%). Conversely, 14 (39%) of the smears were negative for p16 and displayed predominantly reactive changes. However, there was 1 case of high grade squamous intraepithelial lesion showing negative immunostaining for p16. From the view-point of clinical significance, this analysis was highly sensitive (sensitivity, 95%) and specific (specificity, 88%) and had favorable positive (90%) and negative (94%) predictive values.


CONCLUSIONS
On the basis of both morphologic and immunostaining patterns, there was a clear association between strong p16 immunostaining of atypical cells in smears and the presence of significant lesions in the cervix except in 1 patient. Similarly, there was a clear association between lack of p16 expression and absence of cervical lesions. p16 Immunocytochemical stain can be applied successfully to conventional Pap smears and may serve as a useful biomarker in diagnoses of AGC-containing smears. This may offer a more objective parameter to help clarify this ambiguous area of gynecologic cytopathology.
Nieh
Shin
S
Division of Cytopathology, Department of Pathology, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan, Republic of China. niehshin1014@yahoo.com.tw
Chen
Su-Feng
SF
Chu
Tang-Yuan
TY
Lai
Hung-Cheng
HC
Fu
Earl
E
D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis*; D002584:Cervix Uteri / Q000378:metabolism / Q000473:pathology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis* / Q000378:metabolism; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000517:prevention & control*; D004847:Epithelial Cells / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000592:standards; D008875:Middle Aged; D065006:Papanicolaou Test; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D014594:Uterine Neoplasms / Q000378:metabolism / Q000473:pathology*; D014626:Vaginal Smears / Q000592:standards
D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16