Papillary squamous intraepithelial lesions of the uterine cervix: human papillomavirus-dependent changes in cell cycle expression and cytologic features

Most human papillomavirus–associated squamous intraepithelial lesions of the uterine cervix are flat; some have papillary architecture that shows a spectrum of differentiation from low-grade squamous intraepithelial lesions to high-grade squamous intraepithelial lesions. For this subset of lesions, there are few data relating human papillomavirus type to cytology and cell cycle activity. Here, we collected 24 cases of papillary squamous intraepithelial lesions with either low-risk (15 cases) or high-risk (9 cases) human papillomavirus infection. We described their morphology and performed immunohistochemical staining with cell cycle–related markers Ki-67, p53, pRb, and P16INK4a. The Ki-67 labeling index was significantly lower in the low-risk group than in the high-risk group (P < .001). A cut point of less than 50% labeling index detected all but one low-risk group case. Degradation of p53 and pRb was less evident in the low-risk group than in the high-risk group (p53, P < .001; pRb, P = .006). P16INK4a produced an unexpectedly high positive rate of staining in the low-risk group (60%). However, a specific top-heavy distribution pattern was noted, with evident nuclear but faint cytoplasmic staining, whereas the high-risk group showed strong full-thickness nuclear and cytoplasmic staining. The detection of these lesions by smear examination was not reliable, given the wide expression pattern. Papillary structure was evident in none. We conclude that cell cycle–related markers are helpful in distinguishing low- and high-risk lesions. The strong p16INK4a staining in the low-risk group may imply that more cell cycle–controlling pressure is elicited in papillary lesions than in flat lesions. The distribution pattern of p16INK4a staining is important when making a diagnosis; cytology is not effective. Human papillomavirus type, histology, and cell cycle markers could clearly separate these lesions into either a low-risk or a high-risk group, properly designated low-grade squamous intraepithelial lesions or high-grade squamous intraepithelial lesions in current management algorithms. Thus, the previously used terms papillary immature metaplasia and immature condyloma, although descriptive for low-risk group lesions, are confusing and should be discarded.