Fig 1.
PRISMA diagram of the study selection process.
Fig 2.
Subgroups of studies according to the methods used for HER2 positivity determination.
Abbreviations: IHC = Immunohistochemistry, ISH = In Situ Hybridization.
Table 1.
Main characteristics of the included studies.
Fig 3.
Prevalence of HER2 overexpression according to ASCO/CAP-compliant guidelines.
Abbreviations: ASCO = American Society of Clinical Oncology, CAP = College of American Pathologists, DL = Der Simonian and Laird, ME = mixed effects.
Fig 4.
Subgroup analysis by histologic subtype.
All studies. Abbreviations: DL = Der Simonian and Laird, ME = mixed effects.
Fig 5.
Studies that included both squamous and non-squamous histology.
Abbreviations: DL = Der Simonian and Laird, ME = mixed effects.
Fig 6.
Subgroup analysis by World Health Organization geographic region.
Abbreviations: DL = Der Simonian and Laird, ME = mixed effects.
Fig 7.
Subgroup analysis by primary antibody brand.
Abbreviations: DL = Der Simonian and Laird, ME = mixed effects.
Fig 8.
Relationship between the year of study publication, size, and HER2 overexpression prevalence.
Fig 9.
Prevalence of HER2 amplification according to compliance with ASCO/CAP guidelines.
Abbreviations: ASCO = American Society of Clinical Oncology, CAP = College of American Pathologists, DL = Der Simonian and Laird, ME = mixed effects.
Fig 10.
HER2 overexpression prevalence in selected histologic subtypes.
Abbreviations: DL = Der Simonian and Laird, ME = mixed effects.
Table 2.
Summary of the main findings of the review.