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

Area of Science:

• Oncology
• Immunohistochemistry
• Pathology

Background:

• Proliferative activity is a key prognostic factor in solid tumors.
• Ki-67 antibody is a standard for assessing tumor proliferation but is incompatible with formalin-fixed, paraffin-embedded tissues.
• The MIB-1 antibody offers a potential alternative for routinely processed tissues.

Purpose of the Study:

• To evaluate the impact of fixation delay, fixation duration, and microwave heating time on MIB-1 antibody immunoreactivity.
• To determine the optimal conditions for MIB-1 immunostaining in routinely processed tissues.

Main Methods:

• Quantitative image analysis was used to assess MIB-1 immunoreactivity.
• The study examined the effects of varying fixation delay times (0-24 hours), fixation durations (4-48 hours), and microwave heating times.
• Various tumor tissues and tonsil tissue were utilized for the experiments.

Main Results:

• No significant decrease in MIB-1 positive nuclear area was observed with fixation delays up to 8 hours.
• A 24-hour fixation delay showed a minor reduction in positive nuclear area.
• Good MIB-1 immunostaining was achieved with all microwave heating times in tissues fixed for 4 hours.

Conclusions:

• The MIB-1 antibody demonstrates robust immunoreactivity in routinely processed tissues with acceptable fixation delays.
• Microwave heating is effective in optimizing MIB-1 staining.
• MIB-1 is a promising tool for assessing tumor proliferation in standard histopathological samples.