Şahin, Ayşegül A.

The 6th edition of the WHO Classification of Breast Tumours introduces both major and minor changes based on recent advances in our understanding of breast biology, developments in diagnostic modalities, identification of specific molecular targets and new treatment regimens necessitating modifications to pathology reporting and tumour biomarker categorisation. This review summarises the main changes that strive towards a classification of global relevance. In invasive carcinoma, predictive factors increasingly inform modern breast cancer treatment. The 6th edition provides an update on HER2 reporting categories following the DESTINY‐Breast 04 and 06 trials. Terminologies used to classify invasive tumours are clarified, with the term ‘variant’ now reserved for molecular/genetic alterations. Invasive lobular carcinoma (ILC) with extracellular mucin is recognised as a new diagnostic entity with prognostic implications. The diagnosis of mucinous carcinoma (MC) is reserved for mucin secreting carcinomas with grade 1 or 2 morphology and a favourable biomarker profile. The diagnosis of malignant phyllodes tumours requires only four of the original five adverse histological criteria. Classification of neuroendocrine tumours (NETs) is revised, recognising that the unified model, promoted in the 5th edition, is difficult to apply to the breast. New approaches to the classification of adenomyoepithelioma are discussed but the 5th edition system is broadly retained. A new section on ‘Small Diagnostic Samples’ outlines the merits of non‐operative biopsy diagnosis, the B coding system and the importance of multidisciplinary review. Changes to diagnostic practice and the emerging role of artificial intelligence, with advantages and challenges, are discussed in a new section on ‘Digital Pathology’.

Context.— The Nottingham Grading System (NGS) developed by Elston and Ellis is used to grade invasive breast cancer (IBC). Glandular (acinar)/tubule formation is a component of NGS. Objective.— To investigate the ability of pathologists to identify individual structures that should be classified as glandular (acinar)/tubule formation. Design.— A total of 58 hematoxylin-eosin photographic images of IBC with 1 structure circled were classified as tubules (41 cases) or nontubules (17 cases) by Professor Ellis. Images were sent as a PowerPoint (Microsoft) file to breast pathologists, who were provided with the World Health Organization definition of a tubule and asked to determine if a circled structure represented a tubule. Results.— Among 35 pathologists, the κ statistic for assessing agreement in evaluating the 58 images was 0.324 (95% CI, 0.314–0.335). The median concordance rate between a participating pathologist and Professor Ellis was 94.1% for evaluating 17 nontubule cases and 53.7% for 41 tubule cases. A total of 41% of the tubule cases were classified correctly by less than 50% of pathologists. Structures classified as tubules by Professor Ellis but often not recognized as tubules by pathologists included glands with complex architecture, mucinous carcinoma, and the “inverted tubule” pattern of micropapillary carcinoma. A total of 80% of participants reported that they did not have clarity on what represented a tubule. Conclusions.— We identified structures that should be included as tubules but that were not readily identified by pathologists. Greater concordance for identification of tubules might be obtained by providing more detailed images and descriptions of the types of structures included as tubules.

Purpose The seventh edition of the American Joint Committee on Cancer (AJCC) staging system for breast cancer differentiates patients with T1 tumors and lymph node micrometastases (stage IB) from patients with T1 tumors and negative nodes (stage IA). This study was undertaken to determine the utility of the stage IB designation. Patients and Methods The following two cohorts of patients with breast cancer were identified: 3,474 patients treated at The University of Texas MD Anderson Cancer Center from 1993 to 2007 and 4,590 patients from the American College of Surgeons Oncology Group (ACOSOG) Z0010 trial. Clinicopathologic and outcomes data were recorded, and disease was staged according to the seventh edition AJCC staging system. Recurrence-free survival (RFS), disease-specific survival (DSS), and overall survival (OS) were determined using the Kaplan-Meier method and compared using the log-rank test. Results Median follow-up times were 6.1 years and 9.0 years for the MD Anderson Cancer Center and ACOSOG cohorts, respectively. In both cohorts, there were no significant differences between patients with stage IA and stage IB disease in 5- or 10-year RFS, DSS, or OS. Estrogen receptor (ER) status and grade significantly stratified patients with stage I disease with respect to RFS, DSS, and OS. Conclusion Among patients with T1 breast cancer, individuals with micrometastases and those with negative nodes have similar survival outcomes. ER status and grade are better discriminants of survival than the presence of small-volume nodal metastases. In preparing the next edition of the AJCC staging system, consideration should be given to eliminating the stage IB designation and incorporating biologic factors.