Explore the vast range of titles available.

The authors announce the launch of the Consortium for Analytic Standardization in Immunohistochemistry, funded with a grant from the National Cancer Institute. As with other laboratory testing, analytic standards are important for many different stakeholders: commercial vendors of instruments and reagents, biopharmaceutical firms, pathologists, scientists, clinical laboratories, external quality assurance organizations, and regulatory bodies. Analytic standards are customarily central to assay development, validation, and method transfer into routine assays and are critical quality assurance tools. To improve immunohistochemistry (IHC) test accuracy and reproducibility by integrating analytic standards into routine practice. To accomplish this mission, the consortium has 2 mandates: (1) to experimentally determine analytic sensitivity thresholds (lower and upper limits of detection) for selected IHC assays, and (2) to inform IHC stakeholders of what analytic standards are, why they are important, and how and for what purpose they are used. The consortium will then publish the data and offer analytic sensitivity recommendations where appropriate. These mandates will be conducted in collaboration and coordination with clinical laboratories, external quality assurance programs, and pathology organizations. Literature review and published external quality assurance data. Integration of analytic standards is expected to (1) harmonize and standardize IHC assays; (2) improve IHC test accuracy and reproducibility, both within and between laboratories; and (3) dramatically simplify and improve methodology transfer for new IHC protocols from published literature or clinical trials to clinical IHC laboratories.

Inter‐observer concordance data for the HER2 category as assessed by a group of 16 specialist breast pathologists on 50 diagnostic core biopsies was compared with that produced by digital image analysis (DIA) using the HER2 APP, CE2797 (VP APP; Visiopharm, Hoersholm, Denmark). Comparing pathologists' consensus scores and DIA scores, 36 cases (73.5%) agreed. Fleiss' kappa statistic was 0.433 (indicative of moderate agreement). Cohen's weighted kappa was used to compare the scores of individual raters to consensus scores; for all 50 cases the kappa scores had a range between 0.412 and 0.854; the VP APP was ranked 12th of 17 raters (kappa score 0.638 indicating substantial agreement). Results for HER2‐low cases ( N  = 44) showed a kappa score range of 0.295 to 0.823; the VP APP ranked 12th of 17 (score 0.535 indicating moderate agreement). For high agreement cases the kappa score range was 0.664 to 1.000 for all HER2 scores ( N  = 24) and the VP APP scored 0.916 (indicating almost perfect agreement). For the HER2‐low scores ( N  = 20), the kappa score range was 0.506–1.000 and the VP APP scored 0.860 (almost perfect agreement). DIA of the proportions of tumour cells showing expression within each of the HER2 categories demonstrated that the majority of cases showing a low level of agreement between pathologists showed heterogeneity and/or a level of expression close to a cut‐point for decision making. This study demonstrates that the VP APP produces results that are extremely well‐aligned to those of expert pathologists in cases with good overall agreement, and in difficult cases its reproducibility will outperform that of the visual scorer. The results also suggest that use of the VP APP has the potential to reduce the proportion of cases referred for gene amplification testing by reducing the number of cases incorrectly classified as HER2 2+.

PD‐L1 inhibitors are part of first line treatment options for patients with advanced non‐small cell lung cancer. PD‐L1 immunohistochemistry (IHC) assays act as either a companion or a complementary diagnostic. The purpose of this study is to describe the experience of external quality assurance (EQA) provider UK NEQAS ICC and ISH with the comparison of different PD‐L1 assays used in daily practice. Three EQA rounds (pilot, run A and run B) were carried out using formalin fixed paraffin embedded samples with sample sets covering a range of epitope concentrations, including ‘critical samples’ near to clinical threshold cut‐offs. An expert panel (n = 4) evaluated all returned slides simultaneously and independently on a multi‐header microscope together with the participants own in‐house control material. The tonsil sample was evaluated as ‘acceptable’ or ‘unacceptable’, and for the other samples the percentage of PD‐L1 stained tumour cells were estimated in predetermined categories (<1%, 1 to <5%, 5 to <10%, 10 to <25%, 25 to <50%, 50 to <80%, 80 to 100%). In the pilot and the two subsequent runs the number of participating laboratories was 43, 69 and 76, respectively. The pass rate for the pilot run was 67%; this increased to 81% at run A and 82% at run B. For two ‘critical samples’, in runs A and B, 22C3 IHC had significantly higher PD‐L1 expression than SP263 IHC (p < 0.001), whilst the PD‐L1 scores for the other six samples were similar for all assays. In run A the laboratory developed tests (LDTs) using 22C3 scored lower than the commercial 22C3 tests (p = 0.01). After the initial testing, improvement in performance of PD‐L1 IHC is shown for approved and LDT PD‐L1 assays. Equivalency of approved PD‐L1 22C3 and SP263 assays cannot be assumed as the scores cross the clinically relevant thresholds of 1% and 50% PD‐L1 expression.

Breast adenosquamous carcinomas are rare tumours characterized by well-developed gland formation intimately admixed with solid nests of squamous cells immersed in a highly cellular spindle cell stroma. A low-grade variant has been described that is associated with a better prognosis. Here we studied five cases of adenosquamous carcinomas to determine their genetic profiles and to investigate whether the spindle cell component of these cancers could at least in part stem from the glandular/epithelial components. Five adenosquamous carcinomas of the breast were subjected to (1) immunohistochemical analysis, (2) microdissection and genetic analysis with a high-resolution microarray comparative genomic hybridization platform, and (3) chromogenic in situ hybridization. All cases displayed a triple-negative immunophenotype, consistently expressed ‘basal’ keratins and showed variable levels of epidermal growth factor receptor expression. Microarray comparative genomic hybridization analysis of two of the cases revealed multiple low-level gains and losses affecting several chromosomal arms. Case 1 displayed gains of the whole of chromosome 7, and case 2 harboured a focal, high-level amplification of 7p12, encompassing the epidermal growth factor receptor gene, which was associated with strong and intense membranous epidermal growth factor receptor expression. Chromogenic in situ hybridization revealed that the genetic features found in the epithelial cells were also present in a minority of the spindle cells of the stromal component, in particular in those near the epithelial clusters, indicating that some of the spindle cells are clonal and derived from the epithelial component of the tumour. In conclusion, breast adenosquamous carcinomas are triple-negative cancers that express ‘basal’ keratins. These tumours harbour complex genetic profiles. Some of the spindle cells in adenosquamous carcinomas are derived from the epithelial component, suggesting that adenosquamous carcinomas may also be part of the group of metaplastic breast carcinomas with spindle cell metaplastic elements.

Immunocytochemistry (ICC) is central to diagnostic cytopathology, yet achieving consistent staining quality remains challenging owing to technical complexity and limited standardization. External quality assessment (EQA) programs provide an objective framework for benchmarking ICC performance across laboratories. To analyze performance trends, technical variables, and participant self-assessment in the United Kingdom National External Quality Assessment Scheme for Immunocytochemistry and In-Situ Hybridisation (UK NEQAS ICC & ISH) cytopathology module during a 10-year period. Data from 41 EQA runs (June 2014-May 2024) involving 140 laboratories were analyzed. ICC quality on UK NEQAS-provided cytology slides and participant in-house control slides was evaluated by expert assessors using a predefined scoring system (range, 0-20; satisfactory ≥13). Expert scores, participant self-assessment, and assessors' comments were reviewed. Of 14 639 slides assessed, 90.3% achieved satisfactory staining quality, with significant improvement over time. Cell blocks showed higher mean scores and fewer suboptimal results than cytospins (15.77 versus 15.19; P < .001). Fixation influenced performance on in-house controls: methanol-fixed preparations had higher mean scores than formalin-fixed samples (16.36 versus 16.05; P = .003) but a higher suboptimal rate, while acetone- and ethanol-fixed samples performed less well. Inappropriate control selection was a major cause of suboptimal results. Participant self-assessment correlated weakly with expert evaluation (r = .30) and tended to overestimate performance. ICC performance in cytology is generally satisfactory and improving. While cell blocks offer the most robust standardization, optimized methanol fixation represents a viable alternative for non-cell block samples. The discordance between participant self-assessment and expert review highlights the continuing value of EQA in identifying quality gaps and guiding improvement.

Background The aims of this study were to define the distribution of caveolin 2 (CAV2) in frozen and formalin fixed, paraffin embedded (FFPE) normal breast samples and the significance of CAV2 expression in breast cancer. Methods Caveolin 2 distribution in frozen and paraffin-embedded whole tissue sections of normal breast was evaluated using immunohistochemistry and immunofluorescence, in conjunction with antibodies to define luminal epithelial cells (oestrogen receptor and cytokeratin 8/18) and myoepithelial/ basal cells (cytokeratins 14 and 5/6, p63 and smooth muscle actin). CAV2 expression was also immunohistochemically analysed in two independent cohorts of invasive breast carcinomas ( n  = 245 and n  = 418). Results In normal breast, CAV2 was expressed in myoepithelial cells, endothelial cells, fibroblasts and adipocytes. Luminal epithelial cells showed no or only negligible staining. CAV2 expression was observed in 9.6% of all breast cancers and was strongly correlated with high histological grade, lack of oestrogen receptor, progesterone receptor and cyclin D1 expression, and positivity for epidermal growth factor receptor, basal markers, p53 expression, and high proliferation index. Furthermore, CAV2 expression was significantly associated with basal-like immunophenotype and proved to be a prognostic factor for breast cancer-specific survival on univariate analysis. Conclusion Our results demonstrate that CAV2 is preferentially expressed in basal-like cancers and is associated with poor prognosis. Further in vitro studies are required to determine whether CAV2 has oncogenic properties or is only a surrogate marker of basal-like carcinomas.

We describe a collated data set of results from clinical testing of breast cancers carried out between 2009 and 2016 in the United Kingdom and Republic of Ireland. More than 199 000 patient biomarker data sets, together with clinicopathological parameters were collected. Our analyses focused on human epidermal growth factor receptor‐2 (HER2), oestrogen receptor (ER) and progesterone receptor (PR), with the aim of the study being to provide robust confirmatory evidence on known associations in these biomarkers and to uncover new data on previously undescribed or unconfirmed associations, thus strengthening the evidence‐base in clinical breast cancer testing. Overall, 13.1% of tumours were HER2‐positive; 10.6% in ER‐positive tumours, and 25.5% in ER‐negative tumours. Higher rates of HER2 positivity were significantly associated with patient age <56 years versus age ≥56 years, symptomatic versus screen‐detected tumours, testing of involved axillary node versus primary breast cancer, invasive ductal carcinoma (not otherwise specified) versus other histological types, higher histological grade, increasing tumour size, increasing nodal involvement, ER‐negative versus ER‐positive tumour status, PR‐negative versus PR‐positive tumour status. Where ER status was known, 82.7% of tumours were ER‐positive; 80.9% in women age <56 years, and 83.6% in those age ≥56 years (ER‐positive cut‐off ≥1.0% positive tumour cells or equivalent). Where PR status was known, 64.9% of tumours were PR‐positive; 65.8% in women age <56 years, and 64.4% in women age ≥56 years (PR‐positive cut off ≥10.0% or equivalent). These analyses of clinical test results provide contemporary benchmarking data for HER2, ER and PR positive rates.