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The Impact of Phosphohistone-H3-Assisted Mitotic Count and Ki67 Score in the Determination of Tumor Grade and Prediction of Distant Metastasis in Well-Differentiated Pancreatic Neuroendocrine Tumors

Authors
  • Ozturk Sari, Sule1
  • Taskin, Orhun Cig1
  • Gundogdu, Gokcen1
  • Yegen, Gulcin1
  • Onder, Semen1
  • Keskin, Metin2
  • Saglam, Sezer3
  • Ozluk, Yasemin1
  • Gulluoglu, Mine1
  • Mete, Ozgur4, 5
  • 1 Istanbul University, Department of Pathology, Istanbul Faculty of Medicine, Istanbul, Turkey , Istanbul (Turkey)
  • 2 Istanbul University, Department of General Surgery, Istanbul Faculty of Medicine, Istanbul, Turkey , Istanbul (Turkey)
  • 3 University of Bilim, Department of Medical Oncology, Istanbul, Turkey , Istanbul (Turkey)
  • 4 University Health Network, Department of Pathology, Toronto, ON, Canada , Toronto (Canada)
  • 5 University of Toronto, Department of Laboratory Medicine and Pathobiology, Toronto, ON, Canada , Toronto (Canada)
Type
Published Article
Journal
Endocrine Pathology
Publisher
Springer-Verlag
Publication Date
Mar 02, 2016
Volume
27
Issue
2
Pages
162–170
Identifiers
DOI: 10.1007/s12022-016-9424-9
Source
Springer Nature
Keywords
License
Yellow

Abstract

This study investigated the impact of phosphohistone-H3 (PHH3)-assisted mitotic count by comparing its performance with conventional mitotic count and Ki67 score as well as the status of distant metastasis. A total of 43 surgically resected pancreatic neuroendocrine tumors (panNET) with complete follow-up information has been subjected to a standardized assessment with respect to mitotic count (both conventional and PHH3-assisted) and Ki67 score. Five participants assessed mitotic count and the time spent was recorded in both methods. All tumors were assigned to a G1 category of mitotic rate on conventional mitotic count that failed to identify three tumors with a G2 category of mitotic rate on PHH3. Near-perfect and fair agreements were achieved among observers when using PHH3 and conventional method, respectively. The mean time spent to determine mitotic count on PHH3-stained slides was significantly shorter (p < 0.001). The performance of PHH3-assisted mitotic grade category was significant as the three cases with a G2 mitotic category were associated with distant metastasis (p = 0.01). Despite its performance, the PHH3-assisted mitotic count downgraded 17 cases that were classified as G2 based on Ki67 scores in this series. The Ki67 grade category was either the same or higher than the mitotic grade category. Ten patients developed distant metastasis. Eleven tumors exhibited vascular invasion characterized by intravascular tumor cells admixed with thrombus. Our results indicate that PHH3-assisted mitotic count facilitates an accurate mitotic count with a perfect agreement among observers. The small size of this cohort is an important limitation of the current study, a G2 mitotic grade category based on PHH3 immunohistochemistry was one of the correlates of panNETs with distant metastasis. While the prognostic impact of PHH3-assisted mitotic count needs to be clarified in larger cohorts, Ki67 scores designated higher grade category in all cases; thus, it was the best determinant of the tumor grade. More importantly, the presence of vascular invasion along with the Ki67 grade category was found to be independent predictors of distant metastasis.

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