Senologie - Zeitschrift für Mammadiagnostik und -therapie 2018; 15(02): e12-e13
DOI: 10.1055/s-0038-1651703
Abstracts
Georg Thieme Verlag KG Stuttgart · New York

Standardised m-RNA based MammaTyper intrinsic subtyping reliably reproduces St Gallen luminal A and B breast cancer subtypes based on immunohistochemistry and mitotic activity index

K Finsterbusch
1   Dietrich Bonhoeffer Klinikum, Institut für klinische Pathologie, Neubrandenburg, Deutschland
,
T Decker
1   Dietrich Bonhoeffer Klinikum, Institut für klinische Pathologie, Neubrandenburg, Deutschland
,
PJ van Diest
2   University Medical Center Utrecht, Department of Pathology, Utrecht, Niederlande
,
CM Focke
1   Dietrich Bonhoeffer Klinikum, Institut für klinische Pathologie, Neubrandenburg, Deutschland
2   University Medical Center Utrecht, Department of Pathology, Utrecht, Niederlande
› Author Affiliations
Further Information

Publication History

Publication Date:
22 May 2018 (online)

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    Aim:

    Ki67 assessment for intrinsic subtyping of luminal breast cancers (BC) is compromised by variability between labs, observers and methods. MammaTyper is a molecular tool that measures quantitative m-RNA content of ERBB2, ESR1, PGR and MKI67 genes, interprets the results according to the St Gallen 2013 consensus recommendations, and has been shown to be highly reproducible between labs. Our aim was to analyse concordance of luminal A and B rates between MammaTyper and immunohistochemistry (IHC) with Ki67 or mitotic activity index (MAI) in luminal BC.

    Methods:

    101 luminal HER2 negative early BC (UICC I or II) were subtyped as luminal A or B according to the St Gallen consensus 2013 recommendations both by IHC and MammaTyper. Low proliferation was defined as a Ki67-LI < 20% or a MAI < 10/1.59 m2. For Ki67 assessment by IHC, 510 cells were counted according to the International Ki67 in BC Working Group's global (Ki67-G) and hot spot (Ki67-H) methods.

    Results:

    The proportion of luminal A BC was 54% (56/101), 54% (56/101), 36% (36/101), and 56% (57/101) according to MammaTyper, IHC with Ki67-G, IHC with Ki67-H, and IHC plus MAI, respectively. Agreement between MammaTyper and IHC was substantial with MAI (90%, κ 0.78) and Ki67-G (85%, κ 0.68), and moderate with Ki67-H (73%, κ 0.46).

    Conclusion:

    There is a high concordance between m-RNA- and protein-based subtypes of luminal BC which is method dependent for Ki67. Although further validation is needed, the MAI should be considered an alternative marker of proliferation in intrinsic BC subtyping.


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