P16INK4a immunocytochemistry/immunohistochemistry: need for scoring uniformization to be clinically useful in gynecological pathology.

High-risk (HR) human papillomaviruses (HPVs) are the main agents involved in the pathogenesis of cervical preinvasive and invasive lesions. Their regression or persistence is paramount in the progression or regression of preinvasive lesions. Therefore, the diagnosis of the presence or absence of HR-HPV is essential in the prognosis and follow-up of low-grade and high-grade squamous intraepithelial lesions. Human papillomavirus DNA and messenger RNA can be identified by a variety of molecular methods; however, their clinical use has limitations. The fact that p16(INK4a) is a surrogate marker for the presence of HR-HPV is well established. However, the clinical usefulness of p16(INK4a) is currently limited by the lack of immunohistologic and cytologic standardization of a scoring system. This article presents an overview illustrating this shortcoming based on relevant literature data.