Context.—

This article is based on a talk given by the lead author at the 8th Annual Princeton Integrated Pathology Symposium: Breast Pathology, on Sunday April 11, 2021.

Objective.—

To show how the World Health Organization (WHO) Classification of Tumours links to the requirements for quality assurance in breast pathology, including both immunohistochemistry and molecular pathology.

Data Sources.—

The WHO Classification of Tumours 5th edition Breast Tumours entries formed the basis of the talk, together with guidance published by the International Quality Network for Pathology.

Conclusions.—

The WHO Classification of Tumours provides a definitive set of international standards for tumor diagnosis contributed by experts, based on available clinical and research evidence. Techniques used in pathology need internal and external quality assurance to ensure accurate reports for patient management.

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Author notes

The authors have no relevant financial interest in the products or companies described in this article.

Presented in part at the Eighth Princeton Integrated Pathology Symposium; April 11, 2021; virtual.

Competing Interests

The content of this article represents the personal views of the authors and does not represent the views of the authors' employers and associated institutions. Where authors are identified as personnel of the International Agency for Research on Cancer/World Health Organization, the authors alone are responsible for the views expressed in this article and they do not necessarily represent the decisions, policy, or views of the International Agency for Research on Cancer/World Health Organization.