[464] Use of Anti-PhosphohistoneH3 Immunohistochemistry To Determine Mitotic Rate in Melanoma and Its Correlation with the Lymph Node Status

Liaqat Ali, Chad McDonald, Michael D Ioffreda, Loren E Clarke, William Porter, Klaus F Helm. The Penn State Milton S. Hershey Medical Center, Hershey, PA; William Beaumont Hospital, Royal Oak, MI

Background: Mitotic figure (MF) counting is one of the objective criteria for staging of malignant melanomas according to the AJCC staging. Sometimes rarity of MFs in thin melanomas can make the determination of the mitotic index a very time-consuming task. Moreover there is high interobserver variability in differentiating MF from apoptotic cells.
Design: We tested the utility of the mitosis-specific marker phosphohistone-H3 (PHH3) to enhance rapid recognition of MFs and quick reliable staging of melanomas. One hundred and forty archival melanomas representing variable subtypes and Breslow depths were reclassified according to current AJCC criteria based on mitotic counts labelled by PHH3. The slides stained by hematoxylin and eosin and immuno stains were evaluated by two pathologists and two residents.
Results: Anti-PHH3-labeled MFs were easily seen and permitted quick identification of the area(s) of highest mitotic activity. Because of the higher sensitivity of the immunohistochemical stainings for MFs, average mitotic counts per mm2 were higher with PHH3 in contrast with H&E in our study. The precise distinction of MFs from apoptoses and the visualization of the distribution of MFs uncovering mitotic hotspots, even at low magnification, turned out to be major advantages of this mitotic marker and less consumption of pathologist's time to count mitotic figures. To this date we are reporting the largest cohort of melanoma studies with PPH3 staining and correlation of outcome affecting management in terms of lymph node status. We also provide 2-3 years clinical follow up of these patients who developed lymph nodes metastases after the primary diagnosis.
Conclusions: Anti-pHH3 immunostain may prove to be superior to the traditional H&E technique for quantifying mitotic figures in future. However careful interpretation of the stain and awareness of the different stages of mitoses along with pitfalls may be necessary for the pathologist to interpret this immuno stain in the right context.
Category: Dermatopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 124, Wednesday Afternoon


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