Markers to Assist the Diagnosis of Dysplasia and Malignant Transformation

Abstract

Ki-67 is a nonhistone nuclear protein expressed in active cell cycles. The expression of Ki-67 begins in the G1 phase and persists during the active phases of cell cycle throughout the S, G2, and M phases. Ki-67 is undetectable in the G0 phase or in the initial stage of the G1 phase and during DNA repair. The expression of Ki-67 strongly correlates with the intensity of cell proliferation and tumor grade. In routine histopathology, Ki-67 is an important marker for the assessment of cell proliferation. The Ki-67 index is an important criterion for tumor diagnosis (benign, borderline, malignant, low- or high-grade tumor). Furthermore, it is a helpful marker to differentiate between atrophy, thermal alterations, and dysplasia. The irregular accumulation of Ki-67-positive cells in different tissue types would suggest a tendency of the cells to escape the regulation mechanisms. In stratified squamous epithelium, the expression of Ki-67 in more than 30% of the full thickness of the epithelium above the suprabasal layers signifies an abnormal or dysplastic behavior of the epithelium. The Ki-67 index is also an important parameter to distinguish between high-grade and low-grade lymphoma.