Revisiting surgical margins for invasive breast cancer patients treated with breast conservation therapy - Evidence for adopting a 1 mm negative width.

Clinical trials have demonstrated conclusively the non-inferiority of breast-conserving surgery followed by breast radiation therapy (BCT) compared with mastectomy for the treatment of early-stage invasive breast cancer (BC). The definition of the required surgical margin to ensure adequate removal of the cancer by BCT to obtain an acceptable low local recurrence (LR) rate remains controversial. Meta-analyses published by Houssami et al. in 2010 and 2014 demonstrated significantly lower LR rates for patients with a negative margin compared with those with positive (ink on tumour) or close (defined as ≤1 mm or ≤2 mm) margins. Neither meta-analysis addressed whether 'no ink on tumour' was adequate to define a negative margin because of a lack of data. Nevertheless, in 2014, the Society of Surgical Oncology (SSO) and the American Society for Radiation Oncology (ASTRO) with advice from pathologists reviewed these data together and published guidelines recommending that a margin of 'no ink on tumour' was sufficient to define a clear margin in BCT. Subsequently, clinical practice has varied with some national and international bodies endorsing 'no ink on tumour', whilst others have recommended a ≥1 mm margin as acceptable margins for BCT. A more recent meta-analysis conducted by Bundred and colleagues in 2022 did have sufficient data to compare 'no ink on tumour' and 1 mm and concluded that 1 mm rather than 'no ink on tumour', should be used as a minimum negative margin, and recommended that international guidelines be revised. The current review presents a balanced assessment of the evidence relating margin width and local recurrence after BCT. This review concludes that guidelines should consider re-defining a negative margin as ≥1 mm rather than 'no ink on tumour' in the context of BCT, recognising there will be variation to tailor therapy for any individual patient situation to ensure optimal patient care.

The role of the ALKBH5 RNA demethylase in invasive breast cancer.

BACKGROUND: N6-methyladenosine (m6A) is the most common internal RNA modification and is involved in regulation of RNA and protein expression. AlkB family member 5 (ALKBH5) is a m6A demethylase. Given the important role of m6A in biological mechanisms, m6A and its regulators, have been implicated in many disease processes, including cancer. However, the contribution of ALKBH5 to invasive breast cancer (BC) remains poorly understood. The aim of this study was to evaluate the clinicopathological value of ALKBH5 in BC. METHODS: Publicly available data were used to investigate ALKBH5 mRNA alterations, prognostic significance, and association with clinical parameters at the genomic and transcriptomic level. Differentially expressed genes (DEGs) and enriched pathways with low or high ALKBH5 expression were investigated. Immunohistochemistry (IHC) was used to assess ALKBH5 protein expression in a large well-characterised BC series (n = 1327) to determine the clinical significance and association of ALKBH5 expression. RESULTS: Reduced ALKBH5 mRNA expression was significantly associated with poor prognosis and unfavourable clinical parameters. ALKBH5 gene harboured few mutations and/or copy number alternations, but low ALKBH5 mRNA expression was seen. Patients with low ALKBH5 mRNA expression had a number of differentially expressed genes and enriched pathways, including the cytokine-cytokine receptor interaction pathway. Low ALKBH5 protein expression was significantly associated with unfavourable clinical parameters associated with tumour progression including larger tumour size and worse Nottingham Prognostic Index group. CONCLUSION: This study implicates ALKBH5 in BC and highlights the need for further functional studies to decipher the role of ALKBH5 and RNA m6A methylation in BC progression.

What factors influence cellular pathologists' confidence in case reporting?

Histopathology is a challenging interpretive discipline, and the level of confidence a pathologist has in their diagnosis is known to vary, which is conveyed descriptively in pathology reports. There has been little study to accurately quantify pathologists' diagnostic confidence or the factors that influence it. In this study involving sixteen pathologists from six NHS trusts, we assessed diagnostic confidence across multiple variables and four specialties. Each case was reported by four pathologists, with each pathologist reporting each case twice (on light microscopy (LM) and digital pathology (DP)). For each diagnosis, pathologists recorded their confidence on a 7-point Likert scale. This provided 16,187 diagnoses and associated confidence scores for analysis. All variables investigated were found to be significantly predictive of diagnostic confidence, except level of pathologist experience. Confidence was lower for difficult to report cases, cases where there was inter- and intra-pathologist variation in the diagnosis, and cases where the pathologist made an incorrect diagnosis. Confidence was higher, although nominally, for LM diagnoses than DP (rate ratio 1.09 (95% CI 1.01-1.18), p = 0.035), although results indicate pathologists are confident to report on DP. Lowest confidence scores were seen in areas of known diagnostic complexity and cases with quality issues. High confidence in incorrect diagnoses were almost invariably attributed to interpretive diagnostic differences which occurred across both rare and common lesions. The results highlight the value of external quality control schemes and the benefits of selective peer review when reporting.

Prognostic and Clinical Significance of the Proliferation Marker MCM7 in Breast Cancer.

INTRODUCTION: Minichromosome maintenance complex component 7 (MCM7) plays an essential role in proliferation and DNA replication of cancer cells. However, the expression and prognostic significance of MCM7 in breast cancer (BC) remain to be defined. In this study, we aimed to evaluate the role of MCM7 in BC. METHODS: We conducted immunohistochemistry staining of MCM7 in 1,156 operable early-stage BC samples and assessed MCM7 at the transcriptomic levels using publicly available cohorts (n = 13,430). MCM7 expression was evaluated and correlated with clinicopathological parameters including Ki67 labelling index and patient outcome. RESULTS: At the transcriptomic level, there was a significant association between high MCM7 mRNA levels and shorter patient survival in the whole cohort and in luminal BC class but not in the basal-like molecular subtype. High MCM7 protein expression was detected in 43% of patients and was significantly associated with parameters characteristic of aggressive tumour behaviour. MCM7 was independently associated with shorter survival, particularly in oestrogen receptor-positive (luminal) BC. MCM7 stratified luminal tumours with aggressive clinicopathological features into distinct prognostic groups. In endocrine therapy-treated BC patients, high MCM7 was associated with poor outcome, but such association disappeared with administration of adjuvant chemotherapy. Patients with high expression of Ki67 and MCM7 showed worst survival, while patients with double low expression BC showed the best outcome compared with single expression groups. CONCLUSION: The current findings indicate that MCM7 expression has a prognostic value in BC and can be used to identify luminal BC patients who can benefit from adjuvant chemotherapy.

Controversies regarding encapsulated papillary carcinoma of the breast: an approach to evaluation and categorisation.

Malignant papillary lesions, and in particular, encapsulated papillary carcinoma (EPC) of the breast, continue to present diagnostic challenges for the practising pathologist. In addition to the relative rarity of these lesions, the lack of evidence-based diagnostic criteria, differences in the biological characteristics, and the clinical behaviour of in situ and invasive forms, variable use of immunohistochemical markers, and overlap with other tumour types including high-grade circumscribed forms of invasive breast carcinomas has resulted in diagnostic discordance with potentially significant clinical and management implications. Pathologists should be familiar with the range of morphology observed in malignant papillary tumours, EPC, and EPC-like tumours and the existence of tumours with overlapping features. In this review we summarize the common diagnostic pitfalls in malignant papillary tumours and provide an approach to the diagnostic evaluation and categorisation of these enigmatic entities.

The conflicting prognostic role of the stroma-ratio in breast cancer molecular subtypes.

The tumor microenvironment plays a key role in tumor progression. The proportion of the stroma to tumor cells (stroma-tumor ratio (STR)) has a variable prognostic significance in breast cancer (BC) molecular classes. In this study, we evaluated the mechanisms of stroma formation and composition in different molecular subtypes which could explain the different prognostic values. This study interrogated two large well-characterized BC cohorts. Firstly, an in-house BC cohort (n=822) encompassing all BC molecular subtypes from the Nottingham series was used. In each subtype, stromal assessment was carried out and tumors were assigned to two groups: high and low STR, and further correlation with tumor characteristics and patient outcomes was investigated. The contribution of tumor-infiltrating lymphocytes (TILs) to the stroma has also been studied. Secondly, the public domain dataset (The Cancer Genome Atlas data (TCGA), n=978) was used as a validation cohort and for differential gene expression (DGE) analysis. DGE was performed to identify a set of genes associated with high STR in the three main molecular subtypes. High STR was associated with favorable patient outcomes in the whole cohort and in the luminal subtype, whereas high STR showed an association with poor outcome in TNBC. No association with outcome was found in the HER2 enriched BC. DGE analysis identified various pathways in luminal and TNBC subtypes, with immune upregulation and hypoxia pathways enriched in TNBC, and pathways related to fibrosis and stromal remodeling enriched in the luminal group instead. Low STR accompanied by high TILs was shown to carry the most favorable prognosis in TNBC. In line with the DGE results, TILs played a major prognostic role in the stroma of TNBC, but not in the luminal or HER2-enriched subtypes. The underlying molecular mechanisms and composition of the stroma in BC are variable in the molecular subtypes and explain the difference in its prognostic significance.

Stromal lymphocytes are associated with upgrade of B3 breast lesions.

Various histopathological, clinical and imaging parameters have been evaluated to identify a subset of women diagnosed with lesions with uncertain malignant potential (B3 or BIRADS 3/4A lesions) who could safely be observed rather than being treated with surgical excision, with little impact on clinical practice. The primary reason for surgery is to rule out an upgrade to either ductal carcinoma in situ or invasive breast cancer, which occurs in up to 30% of patients. We hypothesised that the stromal immune microenvironment could indicate the presence of carcinoma associated with a ductal B3 lesion and that this could be detected in biopsies by counting lymphocytes as a predictive biomarker for upgrade. A higher number of lymphocytes in the surrounding specialised stroma was observed in upgraded ductal and papillary B3 lesions than non-upgraded (p < 0.01, negative binomial model, n = 307). We developed a model using lymphocytes combined with age and the type of lesion, which was predictive of upgrade with an area under the curve of 0.82 [95% confidence interval 0.77-0.87]. The model can identify some patients at risk of upgrade with high sensitivity, but with limited specificity. Assessing the tumour microenvironment including stromal lymphocytes may contribute to reducing unnecessary surgeries in the clinic, but additional predictive features are needed.

A novel Nav1.5-dependent feedback mechanism driving glycolytic acidification in breast cancer metastasis.

Solid tumours have abnormally high intracellular [Na+]. The activity of various Na+ channels may underlie this Na+ accumulation. Voltage-gated Na+ channels (VGSCs) have been shown to be functionally active in cancer cell lines, where they promote invasion. However, the mechanisms involved, and clinical relevance, are incompletely understood. Here, we show that protein expression of the Nav1.5 VGSC subtype strongly correlates with increased metastasis and shortened cancer-specific survival in breast cancer patients. In addition, VGSCs are functionally active in patient-derived breast tumour cells, cell lines, and cancer-associated fibroblasts. Knockdown of Nav1.5 in a mouse model of breast cancer suppresses expression of invasion-regulating genes. Nav1.5 activity increases ATP demand and glycolysis in breast cancer cells, likely by upregulating activity of the Na+/K+ ATPase, thus promoting H+ production and extracellular acidification. The pH of murine xenograft tumours is lower at the periphery than in the core, in regions of higher proliferation and lower apoptosis. In turn, acidic extracellular pH elevates persistent Na+ influx through Nav1.5 into breast cancer cells. Together, these findings show positive feedback between extracellular acidification and the movement of Na+ into cancer cells which can facilitate invasion. These results highlight the clinical significance of Nav1.5 activity as a potentiator of breast cancer metastasis and provide further evidence supporting the use of VGSC inhibitors in cancer treatment.

Pathological Changes Following Neoadjuvant Endocrine Therapy (NAET): A Multicentre Study of 391 Breast Cancers.

Oestrogen receptor (ER)-positive breast cancer (BC) is generally well responsive to endocrine therapy. Neoadjuvant endocrine therapy (NAET) is increasingly being used for downstaging ER-positive tumours. This study aims to analyse the effect of NAET on a well-characterised cohort of ER-positive BC with particular emphasis on receptor expression. This is a retrospective United Kingdom (UK) multicentre study of 391 patients who received NAET between October 2012 and October 2020. Detailed analyses of the paired pre- and post-NAET morphological changes and hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) expression were performed. The median duration of NAET was 86 days, with median survival and overall survival rates of 380 days and 93.4%, respectively. A total of 90.3% of cases achieved a pathological partial response, with a significantly higher rate of response in the HER2-low cancers. Following NAET, BC displayed some pathological changes involving the tumour stroma including central scarring and an increase in tumour infiltrating lymphocytes (TILs) and tumour cell morphology. Significant changes associated with the duration of NAET were observed in tumour grade (30.6% of cases), with downgrading identified in 19.3% of tumours (p < 0.001). The conversion of ER status from positive to low or negative was insignificant. The conversion of progesterone receptor (PR) and HER2 status to negative status was observed in 31.3% and 38.1% of cases, respectively (p < 0.001). HER2-low breast cancer decreased from 63% to 37% following NAET in the paired samples. Significant morphological and biomarker changes involving PR and HER2 expression occurred following NAET. The findings support biomarker testing on pre-treatment core biopsies and post-treatment residual carcinoma.

The characteristics and prognostic significance of histone H1 expression in breast cancer.

Histone H1 (H.H1) is involved in chromatin organisation and gene regulation and is overexpressed in many malignant tumours, including breast cancer (BC). This study proposed and evaluated the prognostic role of H.H1 expression in BC. H.H1 mRNA expression was evaluated in publicly available BC dataset bc-GenExMiner database (n=4421). H.H1 protein expression was assessed immunohistochemically in a well-characterised early-stage BC cohort (n=1311), and associations with clinicopathological data and survival outcomes were evaluated. At the mRNA level, there was a significant association between high H.H1 mRNA and basal-like BC subtype and with poor outcome. The association with shorter survival was observed in the whole cohort and in the basal-like class. H.H1 protein expression was detected in both tumour cells and surrounding stroma. Total expression was detected in 72% of the cases, including 28% in tumour cell nuclei and 44% in the stroma. There was strong association between high tumour H.H1 expression and triple-negative BC (TNBC) subtype (p=0.007) and with shorter survival (p=0.019), independent of other variables including tumour size, histologic tumour grade, and lymph node status. H.H1 expression is associated with poor prognosis in BC. Given poor prognostic role of H.H1 in TNBC, it may represent a potential therapeutic target for patients with this aggressive disease.

Epitranscriptomic mechanisms of androgen signalling and prostate cancer.

Prostate cancer (PCa) is the second most common cancer diagnosed in men. While radical prostatectomy and radiotherapy are often successful in treating localised disease, post-treatment recurrence is common. As the androgen receptor (AR) and androgen hormones play an essential role in prostate carcinogenesis and progression, androgen deprivation therapy (ADT) is often used to deprive PCa cells of the pro-proliferative effect of androgens. ADTs act by either blocking androgen biosynthesis (e.g. abiraterone) or blocking AR function (e.g. bicalutamide, enzalutamide, apalutamide, darolutamide). ADT is often effective in initially suppressing PCa growth and progression, yet emergence of castrate-resistant PCa and progression to neuroendocrine-like PCa following ADT are major clinical challenges. For this reason, there is an urgent need to identify novel approaches to modulate androgen signalling to impede PCa progression whilst also preventing or delaying therapy resistance. The mechanistic convergence of androgen and epitranscriptomic signalling offers a potential novel approach to treat PCa. The epitranscriptome involves covalent modifications of mRNA, notably, in the context of this review, the N(6)-methyladenosine (m6A) modification. m6A is involved in the regulation of mRNA splicing, stability, and translation, and has recently been shown to play a role in PCa and androgen signalling. The m6A modification is dynamically regulated by the METTL3-containing methyltransferase complex, and the FTO and ALKBH5 RNA demethylases. Given the need for novel approaches to treat PCa, there is significant interest in new therapies that target m6A that modulate AR expression and androgen signalling. This review critically summarises the potential benefit of such epitranscriptomic therapies for PCa patients.

Tripartite Motif-Containing 2, a Glutamine Metabolism-Associated Protein, Predicts Poor Patient Outcome in Triple-Negative Breast Cancer Treated with Chemotherapy.

BACKGROUND: Breast cancer (BC) remains heterogeneous in terms of prognosis and response to treatment. Metabolic reprogramming is a critical part of oncogenesis and a potential therapeutic target. Glutaminase (GLS), which generates glutamate from glutamine, plays a role in triple-negative breast cancer (TNBC). However, targeting GLS directly may be difficult, as it is essential for normal cell function. This study aimed to determine potential targets in BC associated with glutamine metabolism and evaluate their prognostic value in BC. METHODS: The iNET model was used to identify genes in BC that are associated with GLS using RNA-sequencing data. The prognostic significance of tripartite motif-containing 2 (TRIM2) mRNA was assessed in BC transcriptomic data (n = 16,575), and TRIM2 protein expression was evaluated using immunohistochemistry (n = 749) in patients with early-stage invasive breast cancer with long-term follow-up. The associations between TRIM2 expression and clinicopathological features and patient outcomes were evaluated. RESULTS: Pathway analysis identified TRIM2 expression as an important gene co-expressed with high GLS expression in BC. High TRIM2 mRNA and TRIM2 protein expression were associated with TNBC (p < 0.01). TRIM2 was a predictor of poor distant metastasis-free survival (DMFS) in TNBC (p < 0.01), and this was independent of established prognostic factors (p < 0.05), particularly in those who received chemotherapy (p < 0.05). In addition, TRIM2 was a predictor of shorter DMFS in TNBC treated with chemotherapy (p < 0.01). CONCLUSIONS: This study provides evidence of an association between TRIM2 and poor patient outcomes in TNBC, especially those treated with chemotherapy. The molecular mechanisms and functional behaviour of TRIM2 and the functional link with GLS in BC warrant further exploration using in vitro models.

ATF4 as a Prognostic Marker and Modulator of Glutamine Metabolism in Oestrogen Receptor-Positive Breast Cancer.

INTRODUCTION: ATF4, a stress-responsive transcription factor that upregulates adaptive genes, is a potential prognostic marker and modulator of glutamine metabolism in breast cancer. However, its exact role remains to be elucidated. METHODS: ATF4 expression was evaluated at genomic and transcriptomic levels using METABRIC (n = 1,980), GeneMiner (n = 4,712), and KM-Plotter datasets. Proteomic expression was assessed via immunohistochemistry (n = 2,225) in the Nottingham Primary Breast Cancer Series. ATF4 genomic copy number (CN) variation and mRNA/protein in association with clinicopathological parameters, amino acid transporters (AATs), and patient outcome were investigated. RESULTS: Genomic, transcriptomic, and proteomic overexpression of ATF4 was associated with more aggressive ER-negative tumours. ATF4 mRNA and protein expression were significantly associated with increased expression of glutamine related AATs including SLC1A5 (p < 0.01) and SLC7A11 (p < 0.02). High ATF4 and SLC1A5 protein expression was significantly associated with shorter breast cancer-specific survival (p < 0.01), especially in ER+ tumours (p < 0.01), while high ATF4 and SLC7A11 protein expression was associated with shorter survival (p < 0.01). CONCLUSION: These findings suggest a complex interplay between ATF4 and AATs in breast cancer biology and underscore the potential role for ATF4 as a prognostic marker in ER+ breast cancer, offering a unique opportunity for risk stratification and personalized treatment strategies.

Nottingham prognostic x (NPx): a risk stratification tool in ER-positive HER2-negative breast cancer: a validation study.

AIMS: In this study, we validate the use of Nottingham Prognostic x (NPx), consisting of tumour size, tumour grade, progesterone receptor (PR) and Ki67 in luminal BC. MATERIALS AND METHODS: Two large cohorts of luminal early-stage BC (n = 2864) were included. PR and Ki67 expression were assessed using full-face resection samples using immunohistochemistry. NPx was calculated and correlated with clinical variables and outcome, together with Oncotype DX recurrence score (RS), that is frequently used as a risk stratifier in luminal BC. RESULTS: In the whole cohort, 38% of patients were classified as high risk using NPx which showed significant association with parameters characteristics of aggressive tumour behaviour and shorter survival (P < 0.0001). NPx classified the moderate Nottingham Prognostic Index (NPI) risk group (n = 1812) into two distinct prognostic subgroups. Of the 82% low-risk group, only 3.8% developed events. Contrasting this, 14% of the high-risk patients developed events during follow-up. A strong association was observed between NPx and Oncotype Dx RS (P < 0.0001), where 66% of patients with intermediate risk RS who had subsequent distant metastases also had a high-risk NPx. CONCLUSION: NPx is a reliable prognostic index in patients with luminal early-stage BC, and in selected patients may be used to guide adjuvant chemotherapy recommendations.

Human epidermal growth factor receptor 2 (HER2) status in breast cancer: practice points and challenges.

Human epidermal growth factor receptor 2 (HER2)-enriched breast cancer benefits significantly from anti-HER2 targeted therapies. This highlights the critical need for precise HER2 immunohistochemistry (IHC) interpretation serving as a triage tool for selecting patients for anti-HER2 regimens. Recently, the emerging eligibility of patients with HER2-low breast cancers for a novel HER2-targeted antibody-drug conjugate (T-DXd) adds challenges to HER2 IHC scoring interpretation, notably in the 0-1+ range, which shows high interobserver and interlaboratory staining platform variability. In this review, we navigate evolving challenges and suggest practical recommendations for HER2 IHC interpretation.

Morphological and molecular changes of oestrogen receptor-positive breast cancer following bridging endocrine therapy: a United Kingdom multicentre study.

AIMS: Standard neoadjuvant endocrine therapy (NAET) is used for 6-9 months to downstage hormone-receptor-positive breast cancer. Bridging ET was introduced during the COVID-19 pandemic to delay surgical intervention. There are no data in the literature on the effect of short course therapy on tumour response. We aimed to analyse the effect of bridging ET and validate the previously proposed neoadjuvant ET pathological reporting criteria. METHODS AND RESULTS: This was a multicentre cohort of 256 patients who received bridging ET between March and October 2020. Assessment of paired pre- and post-NAET hormone receptors and HER2 and posttherapy Ki67 expression was done. The median duration of NAET was 45 days. In all, 86% of cases achieved partial pathological response and 9% showed minimal residual disease. Histological response to ET was observed from as early as day 6 posttherapy. Central scarring was noted in 32.8% of cases and lymphocytic infiltrate was seen in 43.4% of cases. Significant changes associated with the duration of ET were observed in tumour grade (21%), with downgrading identified in 12% of tumours (P < 0.001), progesterone receptor (PR) expression with switch to PR-negative status in 26% of cases (P < 0.001), and HER2 status with a switch from HER2-low to HER2-negative status in 32% of cases (P < 0.001). The median patient survival was 475 days, with an overall survival rate of 99.6%. CONCLUSIONS: Changes characteristic of tumour regression and significant changes in PR and HER2 occurred following a short course of NAET. The findings support biomarker testing on pretreatment core biopsies and retesting following therapy.

Intraoperative spectroscopic evaluation of sentinel lymph nodes in breast cancer surgery.

BACKGROUND AND OBJECTIVES: Sentinel lymph node (SLN) biopsy is a standard procedure for patients with breast cancer and normal axilla on imaging. Positive SLNs on histological examination can lead to a subsequent surgery for axillary lymph node clearance (ALNC). Here we report a non-destructive technique based on autofluorescence (AF) imaging and Raman spectroscopy for intra-operative assessment of SLNs excised in breast cancer surgery. METHODS: A microscope integrating AF imaging and Raman spectroscopy modules was built to allow scanning of lymph node biopsy samples. During AF-Raman measurements, AF imaging determined optimal sampling locations for Raman spectroscopy measurements. After optimisation of the AF image analysis and training of classification models based on data from 85 samples, the AF-Raman technique was tested on an independent set of 81 lymph nodes comprising 58 fixed and 23 fresh specimens. The sensitivity and specificity of AF-Raman were calculated using post-operative histology as a standard of reference. RESULTS: The independent test set contained 66 negative lymph nodes and 15 positive lymph nodes according to the reference standard, collected from 78 patients. For this set of specimens, the area under the receiver operating characteristic (ROC) curve for the AF-Raman technique was 0.93 [0.83-0.98]. AF-Raman was then operated in a regime that maximised detection specificity, producing a 94% detection accuracy: 80% sensitivity and 97% specificity. The main confounders for SLN metastasis were areas rich in histiocytes clusters, for which only few Raman spectra had been included in the training dataset. DISCUSSION: This preliminary study indicates that with further development and extension of the training dataset by inclusion of additional Raman spectra of histiocytes clusters and capsule, the AF-Raman may become a promising technique for intra-operative assessment of SLNs. Intra-operative detection of positive biopsies could avoid second surgery for axillary clearance.

Deciphering the Clinical Behaviour of Invasive Lobular Carcinoma of the Breast Defines an Aggressive Subtype.

BACKGROUND: Invasive lobular carcinoma (ILC), the most common special type of breast cancer (BC), has unique clinical behaviour and is different from invasive ductal carcinoma of no special type (IDC-NST). However, ILC further comprises a diverse group of tumours with distinct features. This study aims to examine the clinicopathological and prognostic features of different variants of ILC, with a particular focus on characterising aggressive subtypes. METHODS: A large (n = 7140) well-characterised and histologically reviewed BC cohort with treatment and long-term follow-up data was investigated. The cohort was classified based on the WHO classification of tumours into main histological subtypes, including ILC and IDC-NST. ILCs were further classified into variants. Clinicopathological parameters and patient outcomes in terms of BC-specific survival (BCSS) and disease-free survival (DFS) were evaluated. RESULTS: ILC constituted 11% of the cohort. The most common non-classic ILC variants were pleomorphic (pILC) and solid (sILC), constituting 19% of ILC. Compared to classic and related variants (alveolar, trabecular, papillary, and tubulolobular; cILC), pILC and sILC variants were associated with aggressive tumour characteristics. The histologic grade of ILC was an important prognostic variable. The survival patterns identified an aggressive ILC subtype encompassing pILC and high-grade sILC. These tumours, which comprised 14% of the cases, were associated with clinicopathological characteristics of poor prognosis and had high BC-specific death and recurrence rates compared not only to cILC (p < 0.001) but also to IDC-NST (p = 0.02) patients. Contrasting this, cILC patients had significantly longer BCSS and DFS than IDC-NST patients in the first 10 to 15 years of follow-up. Adjuvant chemotherapy did not improve the outcome of patients with aggressive ILC subtypes. CONCLUSIONS: pILC and high-grade sILC variants comprise an aggressive ILC subtype associated with poor prognostic characteristics and a poor response to chemotherapy. These results warrant confirmation in randomised clinical trials.

Clinicopathological Significance of Cyclin-Dependent Kinase 2 (CDK2) in Ductal Carcinoma In Situ and Early-Stage Invasive Breast Cancers.

Cyclin-dependent kinase 2 (CDK2) is a key cell cycle regulator, with essential roles during G1/S transition. The clinicopathological significance of CDK2 in ductal carcinomas in situ (DCIS) and early-stage invasive breast cancers (BCs) remains largely unknown. Here, we evaluated CDK2's protein expression in 479 BC samples and 216 DCIS specimens. Analysis of CDK2 transcripts was completed in the METABRIC cohort (n = 1980) and TCGA cohort (n = 1090), respectively. A high nuclear CDK2 protein expression was significantly associated with aggressive phenotypes, including a high tumour grade, lymph vascular invasion, a poor Nottingham prognostic index (all p-values < 0.0001), and shorter survival (p = 0.006), especially in luminal BC (p = 0.009). In p53-mutant BC, high nuclear CDK2 remained linked with worse survival (p = 0.01). In DCIS, high nuclear/low cytoplasmic co-expression showed significant association with a high tumour grade (p = 0.043), triple-negative and HER2-enriched molecular subtypes (p = 0.01), Comedo necrosis (p = 0.024), negative ER status (p = 0.004), negative PR status (p < 0.0001), and a high proliferation index (p < 0.0001). Tumours with high CDK2 transcripts were more likely to have higher expressions of genes involved in the cell cycle, homologous recombination, and p53 signaling. We provide compelling evidence that high CDK2 is a feature of aggressive breast cancers. The clinical evaluation of CDK2 inhibitors in early-stage BC patients will have a clinical impact.