[785] Mitosis-Specific Marker PHH3 Immunostain Is a More Sensitive and Efficient Method To Evaluate the Mitotic Activity in Gastrointestinal Stromal Tumor (GIST)

Shaobo Zhu, Fan Lin, Zongming Eric Chen. Geisinger Medical Center, Danville, PA

Background: Mitotic activity is an important prognostic factor in GIST. The accurate identification of mitotic figures on the H&E stained slides could be challenging due to processing artifact, degeneration, apoptosis, or lymphocytic infiltration. Mitosis-specific marker PHH3 was proven as a sensitive and reliable method to assess the mitotic activity in various tumors. The aim of the current study was to compare the PHH3-stained mitotic counts and the time for counting on immunostained slides with the mitotic counts and the time for counting on H&E stained slides in GIST.
Design: Immunohistochemical stain for PHH3 and routine H&E staining were performed on 45 cases (41 non-malignant and 4 malignant at the time of sampling) of GIST. The mitotic counts were assessed on both immunostaining slides and H&E stained slides. The PHH3-stained mitotic counts were compared to the mitotic counts on the H&E stained slides. The time to count the mitosis by two methods was recorded too.
Results: For 41 non-malignant GIST cases, the mean mitotic count on the H&E stained slides was 1.9 per 50 high power fields and the mean PHH-stained mitotic count was 4.9 (p < 0.001) per 50 high power fields. For 4 malignant GIST cases, the mean mitotic count on the H&E stained slides was 47.5 per 50 high power fields and the mean PHH-stained mitotic count was 90 per 50 high power fields. The mean time to count the mitotic figures for 50 high power fields on the H&E stained slides was 2 minutes and 50 seconds. The mean time to count the PHH3-stained mitotic figures for 50 high power fields was 40 seconds (p < 0.001).
Conclusions: PHH3 immunostain is a more sensitive and efficient method to evaluate the mitotic activity in GIST. The malignant GISTs demonstrate significant higher mitotic counts by both PHH3 immunostain and H&E stained slides.
Category: Gastrointestinal

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 82, Wednesday Afternoon

 

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