Hans Ikenberg

Screening for Cervical Cancer Precursors With p16/Ki-67 Dual-Stained Cytology: Results of the PALMS Study

Background Pap cytology is known to be more specific but less sensitive than testing for human papillomavirus (HPV) for the detection of high-grade cervical intraepithelial neoplasia (CIN2+). We assessed whether p16/Ki-67 dual-stained cytology, a biomarker combination indicative of transforming HPV infections, can provide high sensitivity for CIN2+ in screening while maintaining high specificity. Results were compared with Pap cytology and HPV testing. Methods A total of 27349 women 18 years or older attending routine cervical cancer screening were prospectively enrolled in five European countries. Pap cytology, p16/Ki-67 immunostaining, and HPV testing were performed on all women. Positive test results triggered colposcopy referral, except for women younger than 30 years with only positive HPV test results. Presence of CIN2+ on adjudicated histology was used as the reference standard. Two-sided bias-corrected McNemar P values were determined. Results The p16/Ki-67 dual-stained cytology positivity rates were comparable with the prevalence of abnormal Pap cytology results and less than 50% of the positivity rates observed for HPV testing. In women of all ages, dual-stained cytology was more sensitive than Pap cytology (86.7% vs 68.5%; P < .001) for detecting CIN2+, with comparable specificity (95.2% vs 95.4%; P = .15). The relative performance of the tests was similar in both groups of women: younger than age 30 and 30 years or older. HPV testing in women 30 years or older was more sensitive than dual-stained cytology (93.3% vs 84.7%; P = .03) but less specific (93.0% vs 96.2%; P < .001). Conclusions The p16/Ki-67 dual-stained cytology combines superior sensitivity and noninferior specificity over Pap cytology for detecting CIN2+. It suggests a potential role of dual-stained cytology in screening, especially in younger women where HPV testing has its limitations.

Morphologic characteristics of p16INK4a-positive cells in cervical cytology samples

OBJECTIVEnOverexpression of p16INK4a has been proposed as a biomarker helpful for the identification of dysplastic cervical epithelial cells on histologic slides as well as in cervical smears. Since a few nontransformed cells in the genital tract in some instances may also express p16INK4a, we evaluated whether applying established morphologic criteria for cervical dysplasia allows a distinction of dysplastic from nondysplastic p16INK4a-stained cells in cytologic samples.nnnSTUDY DESIGNnLiquid-based cytology samples were obtained from a screening population (n=50), and from patients attending a dysplasia clinic (n=40). Slides prepared from these samples were stained with the conventional Papanicolaou stain procedure. From each specimen, a second slide was prepared in parallel and immunostained for p16INK4a. Cytologic diagnoses for most patients attending the dysplasia clinic could be compared to the reported histologic diagnoses on punch biopsy samples taken from the patients at the time of colposcopy. This allowed a comparison of the cytology and p16INK4a immunostaining results with subsequent hematoxylin and eosin-based histologic diagnoses.nnnRESULTSnOverall, in 10% of slides obtained from patients with nonsuspicious smears, few p16INK4a-positive cells were found. Using established morphologic criteria and applying these criteria on cells showing any p16INK4a immunoreactivity, p16INK4a-positive normal or metaplastic cells could be discriminated from p16INK4a-expressing dysplastic cells. In 21 of 22 cases (95%) of high grade lesions (cervical intraepithelial neoplasia 2 or higher in follow-up histology), easily recognizable p16INK4a-positive dysplastic cells could be detected, with the remaining case lacking dysplastic cells in the thin-layer slide used for p16INK4a immunostaining.nnnCONCLUSIONnEstablished morphologic criteria for cervical dysplasia can be readily applied to p16INK4a-immunostained cytologic specimens. Thus, p16INK4a immunostaining may help to avoid ambiguities in the interpretation of cervical cytology samples and facilitate more rapid diagnosis and possibly even automated screening of cytologic slides.

Prospective evaluation of p16/Ki-67 dual-stained cytology for managing women with abnormal Papanicolaou cytology: PALMS study results

Testing for the presence of the human papillomavirus (HPV) is widely accepted for triaging Papanicolaou cytology results categorized as atypical squamous cells of undetermined significance (ASC‐US). In contrast, HPV testing has limited use in triaging cytological low‐grade squamous intraepithelial lesions (LSILs) due to prevalence rates of typically >80%. In the current study, the authors assessed the diagnostic performance of p16/Ki‐67 dual‐stained cytology in triaging ASC‐US and LSIL cases within the prospective, multicentric Primary ASC‐US LSIL Marker Study (PALMS).