Ki-67 Proliferation Marker

Molecular Characteristics

Ki-67 is a nuclear protein that serves as a well-established proliferation marker, present during all active phases of the cell cycle, and its expression is strictly associated with cell proliferation, with distinct cellular localization patterns during interphase and mitosis 1, 2

The American College of Pathologists recommends Ki-67 as a useful marker for estimating the growth fraction and proliferative activity of malignant cells, with the MIB1 monoclonal antibody clone being the "gold standard" for Ki-67 immunohistochemistry in formalin-fixed paraffin-embedded tissue 3, 4
The National Comprehensive Cancer Network notes that the Ki-67 index is the preferred method of establishing proliferative rate in neuroendocrine tumors when accurate mitotic rate is precluded by inadequate tissue 7

Dual-color Ki-67/MART-1 immunohistochemistry specifically detects cell proliferation activity in melanocytes/melanoma cells, and is useful for distinguishing melanomas from benign nevi, differentiating capsular nevi from metastatic melanomas in lymph nodes, and identifying lack of maturation in deep dermal melanocytes 1, 2

The American Society of Clinical Oncology notes that current guidelines indicate that data are insufficient to recommend routine use of Ki-67 to assign breast cancer patients to prognostic groupings for clinical decision-making 6

The College of American Pathologists recommends that tissue storage should be done in a way that prevents loss of Ki-67 immunoreactivity, and that neutral buffered formalin fixation for 4-48 hours is adequate, with antigenicity well preserved in paraffin blocks for decades 3, 5