Comparison of ProEx C with p16INK4a and Ki-67 immunohistochemical staining of cell blocks prepared from residual liquid-based cervicovaginal material: a pilot study.
BACKGROUND
Although liquid-based cervicovaginal cytology has high sensitivity for detecting dysplastic/malignant lesions, many pitfalls exist. Cell blocks can be prepared from residual liquid-based cervicovaginal material and used for immunohistochemistry. The aim of this study was to evaluate a new marker, ProEx C, on cell blocks and its ability to distinguish dysplastic/malignant lesions from morphologically abnormal but benign cells. The results of this study were compared with previously reported results for p16 and Ki-67 on the same material.


METHODS
ProEx C is a cocktail of monoclonal antibodies against proteins associated with aberrant S phase cell cycle induction (topoisomerase IIA, minichromosome maintenance protein 2). ThinPrep (CytycCorp., Boxborough, Mass) cervicovaginal specimens from 79 patients were selected. Four cases had no residual abnormal cells in the cell block. On the basis of the cell block diagnosis, 29 cases were negative for intraepithelial lesion or malignancy (NILM), 27 had low-grade squamous intraepithelial lesions (LSIL), 16 had high-grade squamous intraepithelial lesions (HSIL), and 3 had squamous cell carcinomas (SCC). Cell block sections were immunostained with ProEx C.


RESULTS
Thirteen of 16 (81%) cases of HSIL stained positively with ProEx C. Two of 27 (7%) LSIL stained positively, and 2 (7%) cases of NILM stained positively. All 3 cases of SCC were strongly positive (100%). Staining for ProEx C showed a higher positive predictive value compared with p16.


CONCLUSIONS
ProEx C can be used on cell blocks prepared from residual liquid-based cervicovaginal cytologic specimens. Being a nuclear only stain, it is cleaner and easier to interpret even in scant specimens.
Halloush
Ruba A
RA
Department of Pathology, The Methodist Hospital, Houston, Texas, USA.
Akpolat
Ilkser
I
Jim Zhai
Qihui
Q
Schwartz
Mary R
MR
Mody
Dina R
DR
D000293:Adolescent; D000328:Adult; D000368:Aged; D000951:Antigens, Neoplasm / Q000032:analysis*; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis*; D018797:Cell Cycle Proteins / Q000032:analysis*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis*; D004250:DNA Topoisomerases, Type II / Q000032:analysis*; D004268:DNA-Binding Proteins / Q000032:analysis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000032:analysis*; D008875:Middle Aged; D064111:Minichromosome Maintenance Complex Component 2; D009687:Nuclear Proteins / Q000032:analysis*; D010865:Pilot Projects; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis*; D014626:Vaginal Smears / Q000379:methods*; D002578:Uterine Cervical Dysplasia / Q000175:diagnosis*
D000951:Antigens, Neoplasm; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D019394:Ki-67 Antigen; D009687:Nuclear Proteins; C084859:MCM2 protein, human; D064111:Minichromosome Maintenance Complex Component 2; D004250:DNA Topoisomerases, Type II