Recommendations from the European Commission Initiative on Breast Cancer for multigene testing to guide the use of adjuvant chemotherapy in patients with early breast cancer, hormone receptor positive, HER-2 negative.

BACKGROUND: Predicting the risk of recurrence and response to chemotherapy in women with early breast cancer is crucial to optimise adjuvant treatment. Despite the common practice of using multigene tests to predict recurrence, existing recommendations are inconsistent. Our aim was to formulate healthcare recommendations for the question "Should multigene tests be used in women who have early invasive breast cancer, hormone receptor-positive, HER2-negative, to guide the use of adjuvant chemotherapy?" METHODS: The European Commission Initiative on Breast Cancer (ECIBC) Guidelines Development Group (GDG), a multidisciplinary guideline panel including experts and three patients, developed recommendations informed by systematic reviews of the evidence. Grading of Recommendations Assessment, Development and Evaluation (GRADE) Evidence to Decision frameworks were used. Four multigene tests were evaluated: the 21-gene recurrence score (21-RS), the 70-gene signature (70-GS), the PAM50 risk of recurrence score (PAM50-RORS), and the 12-gene molecular score (12-MS). RESULTS: Five studies (2 marker-based design RCTs, two treatment interaction design RCTs and 1 pooled individual data analysis from observational studies) were included; no eligible studies on PAM50-RORS or 12-MS were identified and the GDG did not formulate recommendations for these tests. CONCLUSIONS: The ECIBC GDG suggests the use of the 21-RS for lymph node-negative women (conditional recommendation, very low certainty of evidence), recognising that benefits are probably larger in women at high risk of recurrence based on clinical characteristics. The ECIBC GDG suggests the use of the 70-GS for women at high clinical risk (conditional recommendation, low certainty of evidence), and recommends not using 70-GS in women at low clinical risk (strong recommendation, low certainty of evidence).

A multicentre analytical comparison study of inter-reader and inter-assay agreement of four programmed death-ligand 1 immunohistochemistry assays for scoring in triple-negative breast cancer.

AIMS: Studies in various cancer types have demonstrated discordance between results from different programmed death-ligand 1 (PD-L1) assays. Here, we compare the reproducibility and analytical concordance of four clinically developed assays for assessing PD-L1-positivity in tumour-infiltrating immune cells in the tumour area (PD-L1-IC-positivity) in triple-negative breast cancer (TNBC). METHODS AND RESULTS: Primary TNBC resection specimens (n = 30) were selected based on their PD-L1-IC-positivity per VENTANA SP142 (<1%: 15 cases; 1-5%: seven cases; >5%: eight cases). Serial histological sections were stained for PD-L1 using VENTANA SP142, VENTANA SP263, DAKO 22C3 and DAKO 28-8. PD-L1-IC-positivity and tumour cell expression (≥1 versus <1%) were scored by trained readers from seven sites using online virtual microscopy. The adjusted mean of PD-L1-IC-positivity for SP263 (7.8%) was significantly higher than those for the other three assays (3.7-4.9%). Differences in adjusted means were statistically significant between SP263 and the other three assays (P < 0.0001) but not between the three remaining assays when excluding SP263 (P = 0.0961-0.6522). Intra-class correlation coefficients revealed moderate-to-strong inter-reader agreement for each assay (0.460-0.805) and poor-to-strong inter-assay agreement for each reader (0.298-0.678) on PD-L1-IC-positivity. CONCLUSIONS: In this first multicentre study of different PD-L1 assays in TNBC, we show that PD-L1-IC-positivity for SP142, 22C3 and 28-8 was reproducible and analytically concordant, indicating that these three assays may be analytically interchangeable. The relevance of the higher PD-L1-IC-positivity for SP263 should be further investigated.

Preoperative breast magnetic resonance imaging in patients with ductal carcinoma in situ: a systematic review for the European Commission Initiative on Breast Cancer (ECIBC).

OBJECTIVE: To evaluate the impact of preoperative MRI in the management of Ductal carcinoma in situ (DCIS). METHODS: We searched the PubMed, EMBASE and Cochrane Library databases to identify randomised clinical trials (RCTs) or cohort studies assessing the impact of preoperative breast MRI in surgical outcomes, treatment change or loco-regional recurrence. We provided pooled estimates for odds ratios (OR), relative risks (RR) and proportions and assessed the certainty of the evidence using the GRADE approach. RESULTS: We included 3 RCTs and 23 observational cohorts, corresponding to 20,415 patients. For initial breast-conserving surgery (BCS), the RCTs showed that MRI may result in little to no difference (RR 0.95, 95% CI 0.90 to 1.00) (low certainty); observational studies showed that MRI may have no difference in the odds of re-operation after BCS (OR 0.96; 95% CI 0.36 to 2.61) (low certainty); and uncertain evidence from RCTs suggests little to no difference with respect to total mastectomy rate (RR 0.91; 95% CI 0.65 to 1.27) (very low certainty). We also found that MRI may change the initial treatment plans in 17% (95% CI 12 to 24%) of cases, but with little to no effect on locoregional recurrence (aHR = 1.18; 95% CI 0.79 to 1.76) (very low certainty). CONCLUSION: We found evidence of low to very low certainty which may suggest there is no improvement of surgical outcomes with pre-operative MRI assessment of women with DCIS lesions. There is a need for large rigorously conducted RCTs to evaluate the role of preoperative MRI in this population. KEY POINTS: • Evidence of low to very low certainty may suggest there is no improvement in surgical outcomes with pre-operative MRI. • There is a need for large rigorously conducted RCTs evaluating the role of preoperative MRI to improve treatment planning for DCIS.

Breast Cancer Screening and Diagnosis: A Synopsis of the European Breast Guidelines.

Description: The European Commission Initiative for Breast Cancer Screening and Diagnosis guidelines (European Breast Guidelines) are coordinated by the European Commission's Joint Research Centre. The target audience for the guidelines includes women, health professionals, and policymakers. Methods: An international guideline panel of 28 multidisciplinary members, including patients, developed questions and corresponding recommendations that were informed by systematic reviews of the evidence conducted between March 2016 and December 2018. GRADE (Grading of Recommendations Assessment, Development and Evaluation) Evidence to Decision frameworks were used to structure the process and minimize the influence of competing interests by enhancing transparency. Questions and recommendations, expressed as strong or conditional, focused on outcomes that matter to women and provided a rating of the certainty of evidence. Recommendations: This synopsis of the European Breast Guidelines provides recommendations regarding organized screening programs for women aged 40 to 75 years who are at average risk. The recommendations address digital mammography screening and the addition of hand-held ultrasonography, automated breast ultrasonography, or magnetic resonance imaging compared with mammography alone. The recommendations also discuss the frequency of screening and inform decision making for women at average risk who are recalled for suspicious lesions or who have high breast density.

[Updated WHO classification of tumors of the breast]. / Aktualisierte WHO-Klassifikation der Tumoren der Mamma.

In the fifth edition of the World Health Organization (WHO) classification of tumors of the breast, the histological features of the lesions continue to form the basis of the classification; however, molecular pathology nowadays provides approaches for improved diagnostics and prediction of prognosis and treatment response, which have been incorporated into the update of the classification. The most important changes are presented, which include changes in the histological classification of invasive carcinomas, the subtyping of lobular carcinoma in situ (LCIS) and the dignity criteria of phyllodes tumors.

[Updated WHO classification of tumors of the breast: the most important changes]. / Aktualisierte WHO-Klassifikation der Tumoren der Mamma: Die wichtigsten Änderungen.

The development of the WHO classification of tumors of the breast is driven by new knowledge from research whose translation into daily practice is considered clinically relevant. The fifth edition represents an update of the fourth edition and essentially follows the previously known systematics. The histologic features of the lesions continue to form the basis of the classification in the update. This also applies to the definition of invasive tumor types. However, several new molecular classifications as well as additional prognostic and predictive factors are presented and discussed, which improve prognosis estimation and therapy decisions. This paper aims to present the main changes in the current WHO classification. These include the revised definition of mixed invasive carcinomas, the introduction of new special invasive entities (tall cell carcinoma with reversed polarity, mucinous cystadenocarcinoma), the deletion of special invasive types and their classification as variants of invasive carcinoma, NST (no special type, including medullary, lipid-rich, glycogen-rich, among others), the typing of primary neuroendocrine neoplasms of the breast by analogy with other organ systems, changes in the dignity criteria of phyllodes tumors, and the revised subtyping of lobular carcinoma in situ (LCIS). In addition to improvements in the fifth edition of the classification, flaws are also highlighted. A section is devoted to new molecular parameters.

Monitoring and evaluation of breast cancer screening programmes: selecting candidate performance indicators.

BACKGROUND: In the scope of the European Commission Initiative on Breast Cancer (ECIBC) the Monitoring and Evaluation (M&E) subgroup was tasked to identify breast cancer screening programme (BCSP) performance indicators, including their acceptable and desirable levels, which are associated with breast cancer (BC) mortality. This paper documents the methodology used for the indicator selection. METHODS: The indicators were identified through a multi-stage process. First, a scoping review was conducted to identify existing performance indicators. Second, building on existing frameworks for making well-informed health care choices, a specific conceptual framework was developed to guide the indicator selection. Third, two group exercises including a rating and ranking survey were conducted for indicator selection using pre-determined criteria, such as: relevance, measurability, accurateness, ethics and understandability. The selected indicators were mapped onto a BC screening pathway developed by the M&E subgroup to illustrate the steps of BC screening common to all EU countries. RESULTS: A total of 96 indicators were identified from an initial list of 1325 indicators. After removing redundant and irrelevant indicators and adding those missing, 39 candidate indicators underwent the rating and ranking exercise. Based on the results, the M&E subgroup selected 13 indicators: screening coverage, participation rate, recall rate, breast cancer detection rate, invasive breast cancer detection rate, cancers > 20 mm, cancers ≤10 mm, lymph node status, interval cancer rate, episode sensitivity, time interval between screening and first treatment, benign open surgical biopsy rate, and mastectomy rate. CONCLUSION: This systematic approach led to the identification of 13 BCSP candidate performance indicators to be further evaluated for their association with BC mortality.

Development and use of health outcome descriptors: a guideline development case study.

BACKGROUND: During healthcare guideline development, panel members often have implicit, different definitions of health outcomes that can lead to misunderstandings about how important these outcomes are and how to balance benefits and harms. McMaster GRADE Centre researchers developed 'health outcome descriptors' for standardizing descriptions of health outcomes and overcoming these problems to support the European Commission Initiative on Breast Cancer (ECIBC) Guideline Development Group (GDG). We aimed to determine which aspects of the development, content, and use of health outcome descriptors were valuable to guideline developers. METHODS: We developed 24 health outcome descriptors related to breast cancer screening and diagnosis for the European Commission Breast Guideline Development Group (GDG). Eighteen GDG members provided feedback in written format or in interviews. We then evaluated the process and conducted two health utility rating surveys. RESULTS: Feedback from GDG members revealed that health outcome descriptors are probably useful for developing recommendations and improving transparency of guideline methods. Time commitment, methodology training, and need for multidisciplinary expertise throughout development were considered important determinants of the process. Comparison of the two health utility surveys showed a decrease in standard deviation in the second survey across 21 (88%) of the outcomes. CONCLUSIONS: Health outcome descriptors are feasible and should be developed prior to the outcome prioritization step in the guideline development process. Guideline developers should involve a subgroup of multidisciplinary experts in all stages of development and ensure all guideline panel members are trained in guideline methodology that includes understanding the importance of defining and understanding the outcomes of interest.

Methods for Development of the European Commission Initiative on Breast Cancer Guidelines: Recommendations in the Era of Guideline Transparency.

Neither breast cancer prevention and early-detection programs, nor their outcomes, are uniform across Europe. This article describes the rationale, methods, and process for development of the European Commission (EC) Initiative on Breast Cancer Screening and Diagnosis Guidelines. To be consistent with standards set by the Institute of Medicine and others, the EC followed 6 general principles. First, the EC selected, via an open call, a panel with broad representation of areas of expertise. Second, it ensured that all recommendations were supported by systematic reviews. Third, the EC separately considered important subgroups of women, included patient advocates in the guidelines development group, and focused on good communication to inform women's decisions. Fourth, EC rules on conflicts of interest were followed and the GRADE (Grading of Recommendations Assessment, Development and Evaluation) Evidence to Decision frameworks were used to structure the process and minimize the influence of competing interests. Fifth, it focused its recommendations on outcomes that matter to women, and certainty of the evidence is rated for each. Sixth, the EC elicited stakeholder feedback to ensure that the recommendations remain up to date and relevant to practice. This article describes the approach and highlights ways of disseminating and adapting the recommendations both within and outside Europe, using innovative information technology tools.

An international reproducibility study validating quantitative determination of ERBB2, ESR1, PGR, and MKI67 mRNA in breast cancer using MammaTyper®.

BACKGROUND: Accurate determination of the predictive markers human epidermal growth factor receptor 2 (HER2/ERBB2), estrogen receptor (ER/ESR1), progesterone receptor (PgR/PGR), and marker of proliferation Ki67 (MKI67) is indispensable for therapeutic decision making in early breast cancer. In this multicenter prospective study, we addressed the issue of inter- and intrasite reproducibility using the recently developed reverse transcription-quantitative real-time polymerase chain reaction-based MammaTyper® test. METHODS: Ten international pathology institutions participated in this study and determined messenger RNA expression levels of ERBB2, ESR1, PGR, and MKI67 in both centrally and locally extracted RNA from formalin-fixed, paraffin-embedded breast cancer specimens with the MammaTyper® test. Samples were measured repeatedly on different days within the local laboratories, and reproducibility was assessed by means of variance component analysis, Fleiss' kappa statistics, and interclass correlation coefficients (ICCs). RESULTS: Total variations in measurements of centrally and locally prepared RNA extracts were comparable; therefore, statistical analyses were performed on the complete dataset. Intersite reproducibility showed total SDs between 0.21 and 0.44 for the quantitative single-marker assessments, resulting in ICC values of 0.980-0.998, demonstrating excellent agreement of quantitative measurements. Also, the reproducibility of binary single-marker results (positive/negative), as well as the molecular subtype agreement, was almost perfect with kappa values ranging from 0.90 to 1.00. CONCLUSIONS: On the basis of these data, the MammaTyper® has the potential to substantially improve the current standards of breast cancer diagnostics by providing a highly precise and reproducible quantitative assessment of the established breast cancer biomarkers and molecular subtypes in a decentralized workup.

Assessing HER2 testing quality in breast cancer: variables that influence HER2 positivity rate from a large, multicenter, observational study in Germany.

Despite >10 years of routine human epidermal growth factor receptor 2 (HER2) testing in breast cancer, testing quality is still an issue. Guidelines recommend assessing HER2 positivity rates as a quality indicator; however, the extent to which patient- or tumor-related factors influence HER2 positivity is still unknown. The present study analyzed these influences to identify pathology centers with HER2 positivity rates unexplained by patient- or tumor-related factors. This observational, prospective study monitored routine HER2 testing at 57 institutes of pathology in Germany (January 2013-August 2014). Data collected included HER2 test result, patient- and tumor-related factors, sample source, and method of sample retrieval. Factors influencing HER2 positivity rates were identified by multiple logistic regression. Individual center effects were assessed in an extended multiple logistic regression model by their statistical significance after adjusting for the combined effect of patient- or tumor-related covariates and multiple testing. Analyses included 15 332 invasive breast cancer samples. Histologic grade showed the strongest influence on HER2 positivity, followed by hormone receptor status, histologic subtype, age, and nodal status (all P<0.0001). The overall HER2 positivity rate across centers was 14.4% (range 7.1-27.3%). A statistically significant center effect on the HER2 positivity rate was identified for three centers (P<0.05), with a trend toward a center effect for a further three (P<0.2). This study, the first of its kind, highlights that assessing HER2 testing quality with HER2 positivity rates should include standardized assessment of patient- or tumor-related characteristics to identify centers with HER2 testing quality issues more effectively. As treatment options for HER2-positive breast cancer continue to evolve, identifying the right patients is key.

Updates in the treatment of ductal carcinoma in situ of the breast.

PURPOSE OF REVIEW: Ductal carcinoma in situ (DCIS) accounts for approximately 20% of mammographically diagnosed breast cancers. Currently, there is a trend to consider DCIS as a lesion for which treatment deescalation is advocated to avoid overtreatment, that is, radiotherapy in addition to breast-conserving surgery or even surgery at all. RECENT FINDINGS: The long-term follow-up updates of the four first-generation randomized trials comparing lumpectomy with and without radiation therapy have confirmed that radiation halves the local failure rates. However, radiotherapy is not associated with a survival benefit just as affirmed by the recently published evaluation of the Surveillance, Epidemiology, and End Results registries database, including 108,196 women with DCIS. Nevertheless, the risk of dying of breast cancer increases about factor 18 after experience of an invasive local recurrence. That means at least some DCIS have the potential to progress to a life threatening disease. At the same time, none of the recently updated prospective trials that tested the outcome after excision alone in low-risk DCIS achieved a 10-year local failure rate below 10%. SUMMARY: DCIS is not a uniform disease. Its clinical behaviour is heterogeneous, but up to date no citeria are available that allow a precise identification of patients with low or very low progression risk who do not need irradiation. Therefore, excision followed by radiotherapy is still the standard of care in patients undergoing breast conservation. Promising new approaches for risk estimation have to be validated prospectively before their use in daily practice can be recommended.

Estrogen receptor alpha (ESR1) gene amplification is frequent in breast cancer.

Using an Affymetrix 10K SNP array to screen for gene copy number changes in breast cancer, we detected a single-gene amplification of the ESR1 gene, which encodes estrogen receptor alpha, at 6q25. A subsequent tissue microarray analysis of more than 2,000 clinical breast cancer samples showed ESR1 amplification in 20.6% of breast cancers. Ninety-nine percent of tumors with ESR1 amplification showed estrogen receptor protein overexpression, compared with 66.6% cancers without ESR1 amplification (P < 0.0001). In 175 women who had received adjuvant tamoxifen monotherapy, survival was significantly longer for women with cancer with ESR1 amplification than for women with estrogen receptor-expressing cancers without ESR1 amplification (P = 0.023). Notably, we also found ESR1 amplification in benign and precancerous breast diseases, suggesting that ESR1 amplification may be a common mechanism in proliferative breast disease and a very early genetic alteration in a large subset of breast cancers.

Sentinel-lymph-node biopsy in patients with breast cancer before and after neoadjuvant chemotherapy (SENTINA): a prospective, multicentre cohort study.

BACKGROUND: The optimum timing of sentinel-lymph-node biopsy for breast cancer patients treated with neoadjuvant chemotherapy is uncertain. The SENTINA (SENTinel NeoAdjuvant) study was designed to evaluate a specific algorithm for timing of a standardised sentinel-lymph-node biopsy procedure in patients who undergo neoadjuvant chemotherapy. METHODS: SENTINA is a four-arm, prospective, multicentre cohort study undertaken at 103 institutions in Germany and Austria. Women with breast cancer who were scheduled for neoadjuvant chemotherapy were enrolled into the study. Patients with clinically node-negative disease (cN0) underwent sentinel-lymph-node biopsy before neoadjuvant chemotherapy (arm A). If the sentinel node was positive (pN1), a second sentinel-lymph-node biopsy procedure was done after neoadjuvant chemotherapy (arm B). Women with clinically node-positive disease (cN+) received neoadjuvant chemotherapy. Those who converted to clinically node-negative disease after chemotherapy (ycN0; arm C) were treated with sentinel-lymph-node biopsy and axillary dissection. Only patients whose clinical nodal status remained positive (ycN1) underwent axillary dissection without sentinel-lymph-node biopsy (arm D). The primary endpoint was accuracy (false-negative rate) of sentinel-lymph-node biopsy after neoadjuvant chemotherapy for patients who converted from cN1 to ycN0 disease during neoadjuvant chemotherapy (arm C). Secondary endpoints included comparison of the detection rate of sentinel-lymph-node biopsy before and after neoadjuvant chemotherapy, and also the false-negative rate and detection rate of sentinel-lymph-node biopsy after removal of the sentinel lymph node. Analyses were done according to treatment received (per protocol). FINDINGS: Of 1737 patients who received treatment, 1022 women underwent sentinel-lymph-node biopsy before neoadjuvant chemotherapy (arms A and B), with a detection rate of 99.1% (95% CI 98.3-99.6; 1013 of 1022). In patients who converted after neoadjuvant chemotherapy from cN+ to ycN0 (arm C), the detection rate was 80.1% (95% CI 76.6-83.2; 474 of 592) and false-negative rate was 14.2% (95% CI 9.9-19.4; 32 of 226). The false-negative rate was 24.3% (17 of 70) for women who had one node removed and 18.5% (10 of 54) for those who had two sentinel nodes removed (arm C). In patients who had a second sentinel-lymph-node biopsy procedure after neoadjuvant chemotherapy (arm B), the detection rate was 60.8% (95% CI 55.6-65.9; 219 of 360) and the false-negative rate was 51.6% (95% CI 38.7-64.2; 33 of 64). INTERPRETATION: Sentinel-lymph-node biopsy is a reliable diagnostic method before neoadjuvant chemotherapy. After systemic treatment or early sentinel-lymph-node biopsy, the procedure has a lower detection rate and a higher false-negative rate compared with sentinel-lymph-node biopsy done before neoadjuvant chemotherapy. These limitations should be considered if biopsy is planned after neoadjuvant chemotherapy. FUNDING: Brustkrebs Deutschland, German Society for Senology, German Breast Group.

Idiopathic Granulomatous Mastitis as a Benign Condition Mimicking Inflammatory Breast Cancer: Current Status, Knowledge Gaps and Rationale for the GRAMAREG Study (EUBREAST-15).

BACKGROUND: Idiopathic granulomatous mastitis (IGM) is a rare, benign inflammatory breast condition often mistaken for inflammatory breast cancer and, therefore, requires a biopsy for accurate diagnosis. Although not cancerous, IGM can cause emotional distress because of severe pain and ensuing breast deformity. Differentiating IGM from other breast inflammations caused by infections is essential. IGM mostly affects premenopausal women and is potentially associated with recent pregnancies and breastfeeding. The risk factors, including smoking and contraceptive use, have inconsistent associations. Steroid responses suggest an autoimmune component, though specific markers are lacking. METHODS: We performed a narrative review on potential risk factors, diagnostics, and therapy of IGM. RESULTS: Diagnostics and clinical management of IGM are challenging. The treatment options include NSAIDs, steroids, surgery, antibiotics, immunosuppressants, prolactin suppressants, and observation, each with varying effectiveness and side effects. CONCLUSIONS: Current IGM treatment evidence is limited, based on case reports and small series. There is no consensus on the optimal management strategy for this disease. The GRAMAREG study by the EUBREAST Study Group aims to collect comprehensive data on IGM to improve diagnostic and treatment guidelines. By enrolling patients with confirmed IGM, the study seeks to develop evidence-based recommendations, enhancing patient care and understanding of this condition.

Global Study on the Accuracy of Human Epidermal Growth Factor Receptor 2-Low Diagnosis in Breast Cancer.

CONTEXT.­: Recently, a new type of antibody-drug conjugate, trastuzumab-deruxtecan (T-DXd), has been approved for the treatment of metastatic breast cancer with low level of human epidermal growth factor receptor 2 (HER2) gene expression. Thereby, eligibility relies on an accurate diagnosis of HER2-low status defined by immunohistochemistry IHC 1+/2+ with no gene amplification. OBJECTIVE.­: To assess pathologists' accuracy and training efficacy in the diagnosis of HER2-low. DESIGN.­: Agreement rates of HER2-low scoring in breast cancer tissue were assessed between expert consensus and real-world pathologists (n = 77 from 14 countries) before and after a specific 4-hour training for HER2-low detection. Two assays were evaluated, the Ventana Pathway 4B5 CDx and the Dako HercepTest (polyclonal). Concordance of the pathologists with consensus score and efficacy of training were measured by Cohen κ, overall rater agreement, and receiver operating characteristic (ROC) curve statistics. RESULTS.­: In the Ventana 4B5 HER2-low category, baseline agreement rates were >80% but <90%. Negative percentage agreement was improved from 80.6% to 91.1% by training. In the HER2-0 category, positive percentage agreement (74.6%) was the only parameter below the 80% benchmark but was significantly improved to 89.2% after training. Training efficacy was confirmed by ROC curve analysis, which shows improvement for the identification of HER2-0 and HER2-low cases. Finally, in-depth examination of cases with discordant HER2 status disclosed specific issues of HER2-low underscoring and overscoring. CONCLUSIONS.­: The ability of pathologists to achieve acceptable diagnostic accuracy in identifying patients with HER2-low breast cancer could be enhanced by short-term training. Potential routes to improve the quality of HER2-low scoring in clinical practice have been identified.

[B3 lesions of the breast: histological, clinical, and epidemiological aspects : Update]. / B3-Läsionen der Mamma: Histologische, klinische und epidemiologische Aspekte : Update.

B3 lesions of the breast are a heterogeneous group of lesions with uncertain malignant potential encompassing a broad spectrum of histologically distinct alterations that often pose challenging decisions if diagnosed on the preoperative core or vacuum biopsies. B3 lesions are mostly detected due to mammographic calcifications or mass lesions and, in most cases, encompass a spectrum of atypical lesions such as atypical ductal hyperplasia, classic lobular neoplasia, flat epithelial atypia, papillomas, fibroepithelial tumors, and rarely other lesions such as mucocele-like lesions, atypical apocrine lesions, and rare stromal proliferations. The use of immunohistochemical stains (estrogen receptors, basal cytokeratin, myoepithelial markers, and stromal marker panel) is useful in the differentiation of these lesions and allowing proper classification. Regarding clinical management of B3 lesions, the radiological-pathological correlation of the given entity plays the most important key element for the proper next diagnostic and therapeutic step.

New treatment options for metastatic HER2-low breast cancer : Consequences for histopathological diagnosis.

The overexpression of HER2 in breast cancer is a classic example for molecular targeted therapy, and it has been shown that classical anti-HER2 therapeutics were only effective in patients with HER2 overexpressing tumors. Therefore, in recent decades, pathologists have been focused on the reliable identification of HER2 overexpressing tumors. Based on the results of recent clinical trials in metastatic breast cancer with antibody-drug conjugates (ADCs), this diagnostic strategy for evaluation of HER2 is currently changing. It has been shown that the ADC trastuzumab-deruxtecan is effective not only against tumors with classical HER2 overexpression, but also against HER2-low tumors. These clinical trial results lead to a paradigm shift in the treatment of patients whose tumours were previously classified as HER2 negative. In addition to the identification of HER2 (score 3+) overexpressing tumors, it is necessary to identify HER2-low expressing tumors (defined as an immunohistochemistry (IHC) score of 1+ or IHC2+ with negative in situ hybridization).Due to the therapeutic consequences, it is important to quickly adapt the diagnostic workup and reporting to the new requirements. In addition, the new therapeutic options for anti-HER2 therapy lead to new challenges for standardization as well as to new scientific questions for the characterization of tumors with low HER2 expression.