Quality control considerations for Ki-67 detection and quantitation in paraffin-embedded tissue.

Proliferative activity has prognostic significance in many solid tumors. Immunohistochemical analysis of tumor proliferation may be accomplished with the Ki-67 monoclonal antibody which recognizes a nuclear antigen expressed throughout the cell cycle. This antibody, however, cannot be used with formalin-fixed, paraffin-embedded tissue. Recently, a Ki-67 equivalent murine monoclonal antibody (MIB-a; AMAC, Inc., Westbrook, ME) was generated which can detect tumor proliferative activity in routinely processed tissue with microwave oven heating. Using quantiative image analysis, we assessed the effect of delay in fixation, total time of formalin fixation, and microwave heating time on the immunoreactivity of this antibody. The effect of time to fixation (0, 2, 4, 8, or 24 hours) on MIB-1 immunostaining was determined in various tumor tissues using image analysis. No significant difference in positive nuclear area was observed for tissues in which fixation was delayed for as long as 8 hours relative to controls. A 24-hour fixation delay resulted in a small decrease in positive nuclear area was observed for tissues in which fixation was delayed for as long as 8 hours relative to controls. A 24-hour fixation delay resulted in a small decrease in positive nuclear area relative to controls. The effect of fixation time (4, 24, or 48 hours) and microwave oven heating time on MIB-1 immunostaining was studied in tonsil tissue, and quantitated by image analysis. Good MIB-1 immunostaining was observed for all microwave oven heating times in tissue fixed for 4 hours.(ABSTRACT TRUNCATED AT 250 WORDS)