Gynecologic Pathology
MIB1 expression in basal cell layer: a diagnostic tool to identify premalignancies of the vulva
p16INK4A and p14ARF expression pattern by immunohistochemistry in human papillomavirus-related cervical neoplasia
MIB1 expression in basal cell layer: a diagnostic tool to identify premalignancies of the vulva
Lichen sclerosus, high-grade usual vulvar intraepithelial neoplasia (VIN) and differentiated VIN have a different malignant potential. The objective of this study was to quantify the proliferative activity in the basal region of the epithelium of vulvar premalignancies. Furthermore, we investigated whether MIB1 expression in the basal region of vulvar epithelium can be helpful in diagnosing differentiated VIN, which may be hard to discern from normal epithelium. MIB1 was used to immunohistochemically visualise proliferating cells within formalin-fixed, paraffin-embedded, archival tissue sections of different vulvar premalignancies (N=48) and normal vulvar epithelium (N=16). Automatic digital image analysis software was developed to quantify the proliferating fraction in different parts of the epithelium (MIB1 positivity index). MIB1 expression differed among the various vulvar premalignancies; a MIB1-negative basal cell layer was a distinct feature of normal vulvar epithelium. No MIB1-negative basal cell layer was noted in differentiated VIN or other vulvar premalignancies. Owing to this negative cell layer, the MIB1 proliferation index in normal vulvar epithelium was significantly lower than in vulvar premalignancies. In conclusion, MIB1 expression can be a helpful tool in diagnosing a premalignancy and has additional value especially to distinguish differentiated VIN neoplasia from normal vulvar epithelium, but cannot explain the differences in malignant potential.
p16INK4A and p14ARF expression pattern by immunohistochemistry in human papillomavirus-related cervical neoplasia
Human papillomavirus is known to play an important etiological role in the genesis of cervical cancer, but only a very small proportion of infected women develop invasive cervical cancer. The purpose of cervical cancer prevention is early diagnosis of its precursors. The molecular detection of human papillomavirus DNA as a diagnostic test to cervical carcinogenesis gave a low positive predictive value as compared to the use of biomarkers. p16INK4A and possibly p14ARF have been proposed as putative surrogate biomarkers that would allow identification of dysplastic cervical epithelia. Serial consecutive biopsies representing normal cervical epithelium to cervical intraepithelial neoplasia and/or invasive cervical cancer were stained with immunohistochemistry for p16INK4A, p14ARF and proliferating cell nuclear antigen. The positive rates of these markers were significantly higher in cervical intraepithelial neoplasia and in squamous cell carcinoma than in normal cervix (P<0.01). No significant difference was noted between lesions progressing from cervical intraepithelial neoplasia to squamous cell carcinoma for both p16INK4A and p14ARF expression (P>0.05). For both biomarkers, nuclear staining was predominantly seen. However, the cytoplasmic stain of p16INK4A increased with disease progression and the pattern of expression varied between different tumors and its location within the lesion. Both nuclear and cytoplasmic staining with p16INK4A and p14ARF of affected epithelial cells were considered positive. In the adjacent normal tissue to cervical neoplasia, the positive rates of p16INK4A, p14ARF and proliferating cell nuclear antigen expression were higher than those found distant to these lesions but the findings did not reach statistical significance. No correlation was seen between the human papillomavirus types detected and the expression of p16INK4a and p14ARF. In conclusion, overexpression of p16INK4A and p14ARF act as potential biomarkers for cervical cancer progression from premalignant lesions.