Invasive lobular carcinoma: an understudied emergent subtype of breast cancer

Invasive lobular breast cancer: Focus on prevention, genetics, diagnosis, and treatment

Invasive lobular cancer (ILC) is the most common of the breast cancer special types, accounting for up to 15% of all breast malignancies. The distinctive biological features of ILC include the loss of the cell adhesion molecule E-cadherin, which drives the tumor's peculiar discohesive growth pattern, with cells arranged in single file and dispersed throughout the stroma. Typically, such tumors originate in the lobules, are more commonly bilateral compared to invasive ductal cancer (IDC) and require a more accurate diagnostic examination through imaging. They are luminal in molecular subtype, and exhibit estrogen and progesterone receptor positivity and HER2 negativity, thus presenting a more unpredictable response to neoadjuvant therapies. There has been a significant increase in research focused on this distinctive breast cancer subtype, including studies on its pathology, its clinical and surgical management, and the high-resolution definition of its genomic profile, as well as the development of new therapeutic perspectives. This review will summarize the heterogeneous pattern of this unique disease, focusing on challenges in its comprehensive clinical management and on future insights and research objectives.

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.

Glucocorticoid receptor-mediated oncogenic activity is dependent on breast cancer subtype

Breast cancer incidence has been steadily rising and is the leading cause of cancer death in women due to its high metastatic potential. Individual breast cancer subtypes are classified by both cell type of origin and receptor expression, namely estrogen, progesterone and human epidermal growth factor receptors (ER, PR and HER2). Recently, the importance and context-dependent role of glucocorticoid receptor (GR) expression in the natural history and prognosis of breast cancer subtypes have been uncovered. In ER-positive breast cancer, GR expression is associated with a better prognosis as a result of ER-GR crosstalk. GR appears to modulate ER-mediated gene expression resulting in decreased tumor cell proliferation and a more indolent cancer phenotype. In ER-negative breast cancer, including GR-positive triple-negative breast cancer (TNBC), GR expression enhances migration, chemotherapy resistance and cell survival. In invasive lobular carcinoma, GR function is relatively understudied, and more work is required to determine whether lobular subtypes behave similarly to their invasive ductal carcinoma counterparts. Importantly, understanding GR signaling in individual breast cancer subtypes has potential clinical implications because of the recent development of highly selective GR non-steroidal ligands, which represent a therapeutic approach for modulating GR activity systemically.

Invasive lobular carcinoma of the breast; clinicopathologic profile and response to neoadjuvant chemotherapy over a 15-year period

INTRODUCTION

Invasive lobular carcinoma (ILC) accounts for 5-15% of invasive breast cancers. Typical ILC is oestrogen receptor (ER) positive and human epidermal growth factor receptor 2 (HER2) negative. Atypical biomarker profiles (ER- and HER2+, ER+ and HER2+ or triple negative) appear to differ from typical ILCs. This study compared subtypes of ILC in terms of clinical and pathological parameters, and response to neoadjuvant chemotherapy (NACT) according to biomarker profile.

METHODS

All patients with ILC treated in a single centre from January 2005 to December 2020 were identified from a prospectively maintained database. Clinicopathologic and outcome data was collected and analysed according to tumour biomarker profile.

RESULTS

A total of 582 patients with ILC were treated. Typical ILC was observed in 89.2% (n = 519) and atypical in 10.8% (n = 63). Atypical ILCs were of a higher grade (35% grade 3 vs 9.6% grade 3, p < 0.001). A larger proportion of atypical ILC received NACT (31.7% vs 6.9% p < 0.001). Atypical ILCs showed a greater response to NACT (mean RCB (Residual Cancer Burden Score) 2.46 vs mean RCB 3.41, p = 0.0365), and higher pathological complete response rates (15% vs 0% p = 0.017). Despite this, overall 5-year disease-free survival (DFS) was higher in patients with typical ILC (91% vs 83%, p = 0.001).

CONCLUSIONS

Atypical ILCs have distinct characteristics. They are more frequently of a higher grade and demonstrate a superior response to NACT. Despite the latter, atypical ILCs have a worse 5-year DFS which should be taken into consideration in terms of prognostication and may assist patient selection for NACT.

Offloading the computational complexity of transfer learning with generic features

Deep learning approaches are generally complex, requiring extensive computational resources and having high time complexity. Transfer learning is a state-of-the-art approach to reducing the requirements of high computational resources by using pre-trained models without compromising accuracy and performance. In conventional studies, pre-trained models are trained on datasets from different but similar domains with many domain-specific features. The computational requirements of transfer learning are directly dependent on the number of features that include the domain-specific and the generic features. This article investigates the prospects of reducing the computational requirements of the transfer learning models by discarding domain-specific features from a pre-trained model. The approach is applied to breast cancer detection using the dataset curated breast imaging subset of the digital database for screening mammography and various performance metrics such as precision, accuracy, recall, F1-score, and computational requirements. It is seen that discarding the domain-specific features to a specific limit provides significant performance improvements as well as minimizes the computational requirements in terms of training time (reduced by approx. 12%), processor utilization (reduced approx. 25%), and memory usage (reduced approx. 22%). The proposed transfer learning strategy increases accuracy (approx. 7%) and offloads computational complexity expeditiously.

Reporting on invasive lobular breast cancer in clinical trials: a systematic review

Invasive lobular breast cancer (ILC) differs from invasive breast cancer of no special type in many ways. Evidence on treatment efficacy for ILC is, however, lacking. We studied the degree of documentation and representation of ILC in phase III/IV clinical trials for novel breast cancer treatments. Trials were identified on Pubmed and clinicaltrials.gov. Inclusion/exclusion criteria were reviewed for requirements on histological subtype and tumor measurability. Documentation of ILC was assessed and ILC inclusion rate, central pathology and subgroup analyses were evaluated. Inclusion restrictions concerning tumor measurability were found in 39/93 manuscripts. Inclusion rates for ILC were documented in 13/93 manuscripts and varied between 2.0 and 26.0%. No central pathology for ILC was reported and 3/13 manuscripts had ILC sub-analyses. ILC is largely disregarded in most trials with poor representation and documentation. The current inclusion criteria using RECIST v1.1, fall short in recognizing the unique non-measurable metastatic infiltration of ILC.

Effect of Ambrosia arborescens Mill. ethanolic extract on breast cancer induced in rats

Background and Aims

Ambrosia arborescens Mill. (A. arborescens) is an aromatic plant used in traditional medicine as an anti-inflammatory, anti-tussive, anti-rheumatic, and anti-diarrheal agent. This study aimed to evaluate the effect of A. arborescens Mill. on a Rattus norvegicus var. albinus-induced breast cancer model.

Materials and Methods

We collected A. arborescens from the province of Julcán, La Libertad Region, Per, and prepared an ethanolic extract using pulverized leaves macerated in 96° ethanol for 72 h with magnetic stirring. In the evaluation of anticancer activity, four experimental groups with 10 female rats each were formed: Group I (Control-7,12-dimethylbenz[a]anthracene [DMBA]), which received DMBA (single dose) and physiological saline solution for 4 months, and Groups II, III, and IV, which received DMBA (single dose) and 200, 400, and 600 mg/kg/day of the ethanolic extract of A. arborescens, respectively, for 4 months.

Results

The DMBA control group presented histological characteristics of ductal carcinoma in situ with necrotic and inflammatory areas, whereas the A. arborescens extract group showed a decrease in tumor volume and recovery of the ductal duct.

Conclusion

Ethanol extract of A. arborescens leaves decreases tumor development in rats with induced breast cancer, and this effect is dose-dependent.

Circulating tumor cells in early lobular versus ductal breast cancer and their associations with prognosis

This is a secondary data analysis of the TIPPING study, which included 1,121 patients with stage I-III breast cancer who had enumeration of CTCs (by either CellSearch or immunomagnetic enrichment and flow cytometry [IE/FC]) and disseminated tumor cells (DTCs) at the time of surgical resection between 1999 and 2012. The primary endpoint was mean number of CTCs by histology, taking into account method of detection and treatment type, and evaluation of histology specific prognostic cutpoints. Overall, patients with ILC had significantly higher CTC counts than those with IDC, a finding which persisted in the 382 patients with CTC enumeration by IE/FC method. Additionally, among those with primary surgery, patients with ILC had significantly higher mean CTC counts than those with IDC (mean 2.11 CTCs/mL versus 0.71 CTCs/mL respectively, p < 0.001), which persisted on multivariate analysis. Patients with ILC and CTC-high/DTC-high status trended towards reduced DRFS HR = 9.27, 95% CI 0.95-90.5, p = 0.055) and had significantly decreased BCSS (HR = 10.4, 95% CI 1.07-99.7, P = 0.043) compared with those who were CTC-low/DTC-low. In the IDC group, CTC-high/DTC-high status was not associated with either DRFS or BCSS. In neoadjvuantly treated patients, there was no significant difference in CTC counts in the ILC group versus the IDC group (mean 0.89 CTCs/mL versus 1.06 CTCs/mL respectively, p = 0.82). Our findings contribute to the limited literature on CTCs and DTCs in ILC, and suggest that clinical utility and optimal thresholds for CTC and DTC assays may differ by histologic subtype in early-stage breast cancer.

Rare Breast Cancer Histotypes-A Retrospective Study and Literature Review

Breast cancer is the most common cancer among women globally and can be classified according to various histological subtypes. Current treatment strategies are typically based on the cancer stage and molecular subtypes. This article aims to address the knowledge gap in the understanding of rare breast cancer. A retrospective study was conducted on 4393 breast cancer patients diagnosed from 1992 to 2012, focusing on five rare subtypes: mucinous, invasive lobular, papillary, mixed invasive and lobular, and pure tubular/cribriform carcinomas. Our analysis, supplemented by a literature review, compared patient characteristics, disease characteristics, and survival outcomes of rare breast cancer patients with invasive carcinoma (not otherwise specified (NOS)). Comparative analysis revealed no significant difference in overall survival rates between these rare cancers and the more common invasive carcinoma (NOS). However, mucinous, papillary, and tubular/cribriform carcinomas demonstrated better disease-specific survival. These subtypes presented with similar characteristics such as early detection, less nodal involvement, more hormonal receptor positivity, and less human epidermal growth factor receptor 2 (HER2) positivity. To conclude, our study demonstrated the diversity in the characteristics and prognosis of rare breast cancer histotypes. Future research should be carried out to investigate histotype-specific management and targeted therapies, given their distinct behavior.

WNT4 Regulates Cellular Metabolism via Intracellular Activity at the Mitochondria in Breast and Gynecologic Cancers

Wnt ligand WNT4 is critical in female reproductive tissue development, with WNT4 dysregulation linked to related pathologies including breast cancer (invasive lobular carcinoma, ILC) and gynecologic cancers. WNT4 signaling in these contexts is distinct from canonical Wnt signaling yet inadequately understood. We previously identified atypical intracellular activity of WNT4 (independent of Wnt secretion) regulating mitochondrial function, and herein examine intracellular functions of WNT4. We further examine how convergent mechanisms of WNT4 dysregulation impact cancer metabolism. In ILC, WNT4 is co-opted by estrogen receptor α (ER) via genomic binding in WNT4 intron 1, while in gynecologic cancers, a common genetic polymorphism (rs3820282) at this ER binding site alters WNT4 regulation. Using proximity biotinylation (BioID), we show canonical Wnt ligand WNT3A is trafficked for secretion, but WNT4 is localized to the cytosol and mitochondria. We identified DHRS2, mTOR, and STAT1 as putative WNT4 cytosolic/mitochondrial signaling partners. Whole metabolite profiling, and integrated transcriptomic data, support that WNT4 mediates metabolic reprogramming via fatty acid and amino acid metabolism. Furthermore, ovarian cancer cell lines with rs3820282 variant genotype are WNT4 dependent and have active WNT4 metabolic signaling. In protein array analyses of a cohort of 103 human gynecologic tumors enriched for patient diversity, germline rs3820282 genotype is associated with metabolic remodeling. Variant genotype tumors show increased AMPK activation and downstream signaling, with the highest AMPK signaling activity in variant genotype tumors from non-White patients. Taken together, atypical intracellular WNT4 signaling, in part via genetic dysregulation, regulates the distinct metabolic phenotypes of ILC and gynecologic cancers.

SIGNIFICANCE

WNT4 regulates breast and gynecologic cancer metabolism via a previously unappreciated intracellular signaling mechanism at the mitochondria, with WNT4 mediating metabolic remodeling. Understanding WNT4 dysregulation by estrogen and genetic polymorphism offers new opportunities for defining tumor biology, precision therapeutics, and personalized cancer risk assessment.

The impact of histologic subtype on primary site surgery in the management of metastatic lobular versus ductal breast cancer: a population based study from the National Cancer Database (NCDB)

PURPOSE

Primary site surgery for metastatic breast cancer improves local control but does not impact overall survival. Whether histologic subtype influences patient selection for surgery is unknown. Given differences in surgical management between early-stage lobular versus ductal disease, we evaluated the impact of histology on primary site surgery in patients with metastatic breast cancer.

METHODS

The National Cancer Database (NCDB, 2010-2016) was queried for patients with stage IV HR-positive, HER2-negative invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC). We compared clinicopathologic features, primary site surgery rates, and outcomes by histologic subtype. Multivariable Cox proportional hazard models with and without propensity score matching were used for overall survival (OS) analyses.

RESULTS

In 25,294 patients, primary site surgery was slightly but significantly less common in the 6,123 patients with ILC compared to the 19,171 patients with IDC (26.9% versus 28.8%, p = 0.004). Those with ILC were less likely to receive chemotherapy (41.3% versus 47.4%, p < 0.0001) or radiotherapy (29.1% versus 37.9%, p < 0.0001), and had shorter OS. While mastectomy rates were similar, those with ILC who underwent lumpectomy had significantly higher positive margin rates (ILC 15.7% versus IDC 11.2%, p = 0.025). In both groups, the odds of undergoing surgery decreased over time, and were higher in younger patients with T2/T3 tumors and higher nodal burden.

CONCLUSION

Lobular histology is associated with less primary site surgery, higher positive margin rates, less radiotherapy and chemotherapy, and shorter OS compared to those with HR-positive HER2-negative IDC. These findings support the need for ILC-specific data and treatment approaches in the setting of metastatic disease.

Fluorine-18-Labeled Fluoroestradiol PET/CT: Current Status, Gaps in Knowledge, and Controversies-AJR Expert Panel Narrative Review

PET/CT using 16α-[18F]-fluoro-17β-estradiol (FES) noninvasively images tissues expressing estrogen receptors (ERs). FES has undergone extensive clinicopathologic validation for ER+ breast cancer and received FDA approval in 2020 for clinical use as an adjunct to biopsy in patients with recurrent or metastatic ER+ breast cancer. Clinical use of FES PET/CT is increasing, but is not widespread in the United States. This AJR Expert Panel Narrative Review explores the present status and future directions of FES PET/CT, including image interpretation, existing and emerging uses, knowledge gaps, and current controversies. Specific controversies discussed include whether both FES PET/CT and FDG PET/CT are warranted in certain scenarios, whether further workup is required after negative FES PET/CT results, whether FES PET/CT findings should inform endocrine therapy selection, and whether immunohistochemistry should remain the standalone reference standard for determining ER status for all breast cancers. Consensus opinions from the panel include agreement with the appropriate clinical uses of FES PET/CT published by a multidisciplinary expert workgroup in 2023; anticipated expanded clinical use of FES PET/CT for staging ER-positive invasive lobular carcinomas and low-grade invasive ductal carcinomas pending ongoing clinical trial results; and the need for further research regarding use of FES PET/CT for ER-expressing nonbreast malignancies.

Is Metastatic Staging Needed for All Patients with Synchronous Bilateral Breast Cancers?

BACKGROUND

Patients with bilateral breast cancers are uncommon and are associated with a poorer prognosis. While metastatic staging guidelines in patients with unilateral cancer were established, the indication of metastatic staging in patients with bilateral breast cancers is unclear. We aimed to determine which patients with synchronous bilateral breast cancers require metastatic staging at diagnosis. This is the first such reported study, to the best of our knowledge.

METHODS

A retrospective review of newly diagnosed synchronous bilateral invasive breast cancer patients at our institution was performed. We excluded patients with malignant phyllodes or no metastatic staging. Patients' demographics and pathological and staging results were analysed to determine the group of bilateral breast cancer patients who required metastatic staging.

RESULTS

A total of 92 patients with synchronous bilateral invasive cancers were included. The mean age was 58 years old, and 64.1% had bilateral invasive ductal carcinoma. 23.9% had systemic metastasis. Nodal status was statistically significant for systemic metastasis on staging (p = 0.0081), with only three patients (3.3%) having negative nodal status and positive metastatic staging. These three patients, however, showed symptoms of distant metastasis. 92.3% of patients with negative nodes also had negative metastatic staging. Using negative nodal status as a guide avoided metastatic staging in 40.4% of all patients.

CONCLUSIONS

Negative nodal status was the most predictive factor for no systemic metastasis on staging in patients with synchronous bilateral invasive breast cancers. Hence, metastatic staging could be reserved for patients with symptoms of systemic metastasis and/or metastatic nodes. This finding could be validated in larger studies.

Effect of histological breast cancer subtypes invasive lobular versus non-special type on survival in early intermediate-to-high-risk breast carcinoma: results from the SUCCESS trials

BACKGROUND

Invasive lobular breast carcinomas (ILC) have different histological features compared to non-special type carcinomas (NST), but the effect of histological subtypes on survival is controversial. In this study, we compared clinicopathological characteristics and outcomes between ILC and NST based on a large pooled data set from three adjuvant breast cancer trials (SUCCESS A, B, and C) and investigated a potential differential effect of recurrence risk related to nodal stage on survival.

METHODS

From 2005 to 2017, the large randomized controlled SUCCESS A, B, and C trials enrolled 8190 patients with primary, intermediate-to-high-risk breast carcinoma. All patients received adjuvant chemotherapy, and endocrine and/or HER2-targeted treatment was given where appropriate. Survival outcomes in terms of disease-free survival (DFS), overall survival (OS), breast cancer-specific survival (BCSS), and distant disease-free survival (DDFS) were estimated using the Kaplan-Meier method and analyzed using log-rank tests as well as univariable and adjusted multivariable Cox regression models.

RESULTS

In the SUCCESS trials, 6284 patients had NST and 952 had ILC. The median follow-up time was 64 months. ILC patients were older, more likely to receive mastectomy, and more likely to have larger tumor sizes, lymph node infiltration, hormone receptor-positive, HER2neu-negative, and luminal A-like tumors than NST patients. In the overall cohort, no significant differences between ILC and NST were detectable regarding the four survival endpoints, with hazard ratios obtained in adjusted multivariable cox regressions of 0.96 (95% CI 0.77-1.21, p = 0.743) for DFS, 1.13 (95% CI 0.85-1.50, p = 0.414) for OS, 1.21 (95% CI 0.89-1.66, p = 0.229) for BCSS, and 0.95 (95% CI 0.73-1.24, p = 0.689) for DDFS. However, a differential effect of nodal stage on survival was observed, with better survival for ILC patients with pN0/pN1 tumors and worse survival for ILC patients with pN2/pN3 tumors compared to NST patients.

CONCLUSIONS

Our results revealed that ILC was associated with worse survival compared to NST for patients at high risk of recurrence due to advanced lymph node infiltration. These findings should be taken into account for treatment decisions and monitoring.

Bispecific antibodies revolutionizing breast cancer treatment: a comprehensive overview

Breast cancer (BCa) is known as a complex and prevalent disease requiring the development of novel anticancer therapeutic approaches. Bispecific antibodies (BsAbs) have emerged as a favorable strategy for BCa treatment due to their unique ability to target two different antigens simultaneously. By targeting tumor-associated antigens (TAAs) on cancer cells, engaging immune effector cells, or blocking critical signaling pathways, BsAbs offer enhanced tumor specificity and immune system involvement, improving anti-cancer activity. Preclinical and clinical studies have demonstrated the potential of BsAbs in BCa. For example, BsAbs targeting human epidermal growth factor receptor 2 (HER2) have shown the ability to redirect immune cells to HER2-positive BCa cells, resulting in effective tumor cell killing. Moreover, targeting the PD-1/PD-L1 pathway by BsAbs has demonstrated promising outcomes in overcoming immunosuppression and enhancing immune-mediated tumor clearance. Combining BsAbs with existing therapeutic approaches, such as chemotherapy, targeted therapies, or immune checkpoint inhibitors (ICIs), has also revealed synergistic effects in preclinical models and early clinical trials, emphasizing the usefulness and potential of BsAbs in BCa treatment. This review summarizes the latest evidence about BsAbs in treating BCa and the challenges and opportunities of their use in BCa.

Digital mammography and digital breast tomosynthesis for detecting invasive lobular and ductal carcinoma

PURPOSE

Invasive lobular carcinoma (ILC) is a distinct histological subtype of breast cancer that can make early detection with mammography challenging. We compared imaging performance of digital breast tomosynthesis (DBT) to digital mammography (DM) for diagnoses of ILC, invasive ductal carcinoma (IDC), and invasive mixed carcinoma (IMC) in a screening population.

METHODS

We included screening exams (DM; n = 1,715,249 or DBT; n = 414,793) from 2011 to 2018 among 839,801 women in the Breast Cancer Surveillance Consortium. Examinations were followed for one year to ascertain incident ILC, IDC, or IMC. We measured cancer detection rate (CDR) and interval invasive cancer rate/1000 screening examinations for each histological subtype and stratified by breast density and modality. We calculated relative risk (RR) for DM vs. DBT using log-binomial models to adjust for the propensity of receiving DBT vs. DM.

RESULTS

Unadjusted CDR per 1000 mammograms of ILC overall was 0.33 (95%CI: 0.30-0.36) for DM; 0.45 (95%CI: 0.39-0.52) for DBT, and for women with dense breasts- 0.33 (95%CI: 0.29-0.37) for DM and 0.54 (95%CI: 0.43-0.66) for DBT. Similar results were noted for IDC and IMC. Adjusted models showed a significantly increased RR for cancer detection with DBT compared to DM among women with dense breasts for all three histologies (RR; 95%CI: ILC 1.53; 1.09-2.14, IDC 1.21; 1.02-1.44, IMC 1.76; 1.30-2.38), but no significant increase among women with non-dense breasts.

CONCLUSION

DBT was associated with higher CDR for ILC, IDC, and IMC for women with dense breasts. Early detection of ILC with DBT may improve outcomes for this distinct clinical entity.

Lobular Carcinoma of the Breast: A Comprehensive Review with Translational Insights

The second most common breast carcinoma, invasive lobular carcinoma, accounts for approximately 15% of tumors of breast origin. Its incidence has increased in recent times due in part to hormone replacement therapy and improvement in diagnostic modalities. Although believed to arise from the same cell type as their ductal counterpart, invasive lobular carcinomas (ILCs) are a distinct entity with different regulating genetic pathways, characteristic histologies, and different biology. The features most unique to lobular carcinomas include loss of E-Cadherin leading to discohesion and formation of a characteristic single file pattern on histology. Because most of these tumors exhibit estrogen receptor positivity and Her2 neu negativity, endocrine therapy has predominated to treat these tumors. However novel treatments like CDK4/6 inhibitors have shown importance and antibody drug conjugates may be instrumental considering newer categories of Her 2 Low breast tumors. In this narrative review, we explore multiple pathological aspects and translational features of this unique entity. In addition, due to advancement in technologies like spatial transcriptomics and other hi-plex technologies, we have tried to enlist upon the characteristics of the tumor microenvironment and the latest associated findings to better understand the new prospective therapeutic options in the current era of personalized treatment.

Analysis of prognosis in different subtypes of invasive lobular carcinoma using the Japanese National Cancer Database-Breast Cancer Registry

PURPOSE

Many studies have shown that the prognosis of invasive lobular carcinoma (ILC) is better than that of invasive ductal carcinoma (IDC). However, both disorders exhibit different prognoses according to molecular subtype, and the prognosis of ILC subtypes might depend on their hormone receptor positivity rate. This study clarified the prognosis of ILC and IDC in each subtype and examined the effectiveness of adjuvant chemotherapy (CT) in luminal ILC.

METHODS

We planned the analysis using data from the Breast Cancer Registry in Japan. Because it was presumed that there are differences in characteristics between ILC and IDC, we created matched cohorts using exact matching to compare their prognoses. We compared the prognosis of ILC and IDC for each subtype. We also compared the prognosis of luminal ILC between the CT and non-CT groups.

RESULTS

For all subtypes, the disease-free survival (DFS) and overall survival (OS) of ILC were poorer than those of IDC. In the analysis by each subtype, no statistically significant difference was found in DFS and OS in luminal human epidermal growth factor 2 (HER2), HER2, and triple-negative cohorts; however, luminal ILC had significantly poorer DFS and OS than luminal IDC. The CT effects on the prognosis of luminal ILC were greater in more advanced cases.

CONCLUSION

Luminal ILC had a poorer prognosis than luminal IDC, contributing to the worse prognosis of ILC than that of IDC in the overall cohort. Different therapeutic approaches from luminal IDC are essential for a better prognosis of luminal ILC.

Glucocorticoid Receptor Activation in Lobular Breast Cancer Is Associated with Reduced Cell Proliferation and Promotion of Metastases

Estrogen receptor-positive (ER+) invasive lobular breast cancer (ILC) comprises about ~15% of breast cancer. ILC's unique genotypic (loss of wild type E-cadherin expression) and phenotypic (small individual round cancer cells that grow in discontinuous nests) are thought to contribute to a distinctive pattern of metastases to serosal membranes. Unlike invasive ductal carcinoma (IDC), ILC metastases often intercalate into the mesothelial layer of the peritoneum and other serosal surfaces. While ER activity is a known driver of ILC proliferation, very little is known about how additional nuclear receptors contribute to ILC's distinctive biology. In ER+ IDC, we showed previously that glucocorticoid receptor (GR) activity inhibits pro-proliferative gene expression and cell proliferation. Here we examined ER+ ILC models and found that GR activation similarly reduces S-phase entry gene expression and ILC proliferation. While slowing tumor growth rate, our data also suggest that GR activation results in an enhanced metastatic phenotype through increasing integrin-encoding gene expression, extracellular matrix protein adhesion, and mesothelial cell clearance. Moreover, in an intraductal mouse mammary gland model of ILC, we found that GR expression is associated with increased bone metastases despite slowed primary mammary tumor growth. Taken together, our findings suggest GR-mediated gene expression may contribute to the unusual characteristics of ILC biology.

Area Deprivation Index in Patients with Invasive Lobular Carcinoma of the Breast: Associations with Tumor Characteristics and Outcomes

BACKGROUND

Although investigators have shown associations between socioeconomic status (SES) and outcomes in breast cancer, there is a paucity of such data for invasive lobular carcinoma (ILC), the second most common type of breast cancer. Herein we evaluated the relationship between SES with tumor features and outcomes in stage I to III patients with ILC.

METHODS

We analyzed a prospectively maintained institutional ILC database and utilized the area deprivation index (ADI) to determine neighborhood adversity, an indicator of SES. We used Cox proportional hazards models in Stata 17.0 to evaluate relationships between ADI quintile (Q), race, body mass index (BMI), clinicopathologic features, treatment type, and event-free survival (EFS).

RESULTS

Of 804 patients with ILC, 21.4% lived in neighborhoods classified as ADI Q1 (least resource-deprived) and 19.7% in Q5 (most resource-deprived). Higher deprivation was significantly associated with larger tumor size (3.6 cm in Q5 vs. 3.1 cm in Q1), increased presence of lymphovascular invasion (8.9% in Q5 vs. 6.7% in Q1), and decreased use of adjuvant endocrine therapy (67.1% in Q5 vs. 73.6% in Q1). On multivariable analysis, tumor size, receptor subtypes, and omission of adjuvant endocrine therapy were associated with reduced EFS.

CONCLUSIONS

These data show that patients with ILC and higher ADI experience more aggressive tumors and differences in treatment. More data evaluating the complex relationships between these factors is needed to optimize outcomes for patients with ILC, regardless of SES.

IMPACT

ADI is associated with differences in patients with ILC.

The impact of histologic subtype on primary site surgery in the management of metastatic lobular versus ductal breast cancer: a population based study from the National Cancer Database

Purpose

Primary site surgery for metastatic breast cancer improves local control but does not impact overall survival. Whether histologic subtype influences patient selection for surgery is unknown. Given differences in surgical management between early-stage lobular versus ductal disease, we evaluated the impact of histology on primary site surgery in patients with metastatic breast cancer.

Methods

The National Cancer Database (NCDB, 2010-2016) was queried for patients with stage IV HR-positive, HER2-negative invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC). We compared clinicopathologic features, primary site surgery rates, and outcomes by histologic subtype. Multivariable Cox proportional hazard models with and without propensity score matching were used for overall survival (OS) analyses.

Results

In 25,294 patients, primary site surgery was slightly but significantly less common in the 6,123 patients with ILC compared to the 19,171 patients with IDC (26.9% versus 28.8%, p = 0.004). Those with ILC were less likely to receive chemotherapy (41.3% versus 47.4%, p < 0.0001) or radiotherapy (29.1% versus 37.9%, p < 0.0001), and had shorter OS. While mastectomy rates were similar, those with ILC had more positive margins (10.6% versus 8.3%, p = 0.005). In both groups, the odds of undergoing surgery decreased over time, and were higher in younger patients with T2/T3 tumors and higher nodal burden.

Conclusion

Lobular histology is associated with less primary site surgery, higher positive margin rates, less radiotherapy and chemotherapy, and shorter OS compared to those with HR-positive HER2-negative IDC. These findings support the need for ILC-specific data and treatment approaches in the setting of metastatic disease.

Characterization of Breast Tumors from MR Images Using Radiomics and Machine Learning Approaches

Determining histological subtypes, such as invasive ductal and invasive lobular carcinomas (IDCs and ILCs) and immunohistochemical markers, such as estrogen response (ER), progesterone response (PR), and the HER2 protein status is important in planning breast cancer treatment. MRI-based radiomic analysis is emerging as a non-invasive substitute for biopsy to determine these signatures. We explore the effectiveness of radiomics-based and CNN (convolutional neural network)-based classification models to this end. T1-weighted dynamic contrast-enhanced, contrast-subtracted T1, and T2-weighted MR images of 429 breast cancer tumors from 323 patients are used. Various combinations of input data and classification schemes are applied for ER⁺ vs. ER^-, PR⁺ vs. PR^-, HER2⁺ vs. HER2^-, and IDC vs. ILC classification tasks. The best results were obtained for the ER⁺ vs. ER^- and IDC vs. ILC classification tasks, with their respective AUCs reaching 0.78 and 0.73 on test data. The results with multi-contrast input data were generally better than the mono-contrast alone. The radiomics and CNN-based approaches generally exhibited comparable results. ER and IDC/ILC classification results were promising. PR and HER2 classifications need further investigation through a larger dataset. Better results by using multi-contrast data might indicate that multi-parametric quantitative MRI could be used to achieve more reliable classifiers.

PD-L1 blockade in combination with carboplatin as immune induction in metastatic lobular breast cancer: the GELATO trial

Invasive lobular breast cancer (ILC) is the second most common histological breast cancer subtype, but ILC-specific trials are lacking. Translational research revealed an immune-related ILC subset, and in mouse ILC models, synergy between immune checkpoint blockade and platinum was observed. In the phase II GELATO trial ( NCT03147040 ), patients with metastatic ILC were treated with weekly carboplatin (area under the curve 1.5 mg ml-1 min-1) as immune induction for 12 weeks and atezolizumab (PD-L1 blockade; triweekly) from the third week until progression. Four of 23 evaluable patients had a partial response (17%), and 2 had stable disease, resulting in a clinical benefit rate of 26%. From these six patients, four had triple-negative ILC (TN-ILC). We observed higher CD8+ T cell infiltration, immune checkpoint expression and exhausted T cells after treatment. With this GELATO trial, we show that ILC-specific clinical trials are feasible and demonstrate promising antitumor activity of atezolizumab with carboplatin, particularly for TN-ILC, and provide insights for the design of highly needed ILC-specific trials.

The Great Immune Escape: Understanding the Divergent Immune Response in Breast Cancer Subtypes

Breast cancer, the most common type of cancer affecting women, encompasses a collection of histologic (mainly ductal and lobular) and molecular subtypes exhibiting diverse clinical presentation, disease trajectories, treatment options, and outcomes. Immunotherapy has revolutionized treatment for some solid tumors but has shown limited promise for breast cancers. In this review, we summarize recent advances in our understanding of the complex interactions between tumor and immune cells in subtypes of breast cancer at the cellular and microenvironmental levels. We aim to provide a perspective on opportunities for future immunotherapy agents tailored to specific features of each subtype of breast cancer.

SIGNIFICANCE

Although there are currently over 200 ongoing clinical trials testing immunotherapeutics, such as immune-checkpoint blockade agents, these are largely restricted to the triple-negative and HER2+ subtypes and primarily focus on T cells. With the rapid expansion of new in vitro, in vivo, and clinical data, it is critical to identify and highlight the challenges and opportunities unique for each breast cancer subtype to drive the next generation of treatments that harness the immune system.

Histology-based survival outcomes in hormone receptor-positive metastatic breast cancer treated with targeted therapies

The addition of targeted therapies (TT) to endocrine therapy (ET) has improved the outcomes of patients with HR-positive, HER2-negative metastatic breast cancer (mBC). However, it is unknown whether patients with invasive lobular carcinoma (ILC) or mixed invasive ductal and lobular carcinoma (mixed) histologies experience the same magnitude of benefit from this therapy as those with invasive ductal carcinoma (IDC). We aim to determine whether patients with IDC, ILC, and mixed HR+/HER2- mBC derive similar benefit from the addition of cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6is), mammalian target of rapamycin inhibitor (mTORi), and phosphoinositide 3-kinase inhibitor (PI3Ki) to ET in HR+/HER2- mBC. We conducted an observational, population-based investigation using data from the MD Anderson prospectively collected database. We conducted a histology-based analysis of progression-free survival (PFS) and overall survival (OS) durations in 3784 patients with HR+/HER2- mBC who were treated with TT plus ET between January 1, 2010, and December 31, 2021. Out of the 3784 patients, 2975 were included in the final analysis. Of these, 2249 received CDK4/6is (81% IDC, 15% ILC, and 4% mixed), 1027 received everolimus (82% IDC, 14% ILC, and 4% mixed) and 49 received alpelisib (81% IDC and 19% ILC). The addition of targeted therapy to ET did not result in statistically significant differences in PFS or OS duration among patients with IDC, ILC, and mixed HR+/HER2- mBC. We concluded that for patients with HR+/HER2- mBC, the addition of TT to ET leads to a similar magnitude of benefit, irrespective of histology.

The Impact of Chemotherapy Prescription on Long-Term Survival Outcomes in Early-Stage Invasive Lobular Carcinoma - A Systematic Review and Meta-Analysis

INTRODUCTION

Invasive lobular carcinoma (ILCs) are typically endocrine responsive breast cancers which respond poorly to chemotherapy. The long-term survival advantage of prescribing chemotherapy in such cases remains unclear. To perform a systematic review and meta-analysis assessing, the impact of prescribing chemotherapy in such patients on long-term disease-free (DFS) and overall (OS) survival outcomes.

METHODS

A systematic review and meta-analysis was performed in accordance with the PRISMA guidelines. Ten-year DFS and OS were pooled as odds ratios (ORs) with 95% confidence intervals (CI) using the Mantel-Haenszel method. Time-to-effect modelling was performed using the generic inverse variance method.

RESULTS

Overall, 9 studies including 28,218 patients were included. The mean follow-up was 74 months (range: 0-150 months) and mean age was 60 years (range: 22-90 years). Of these, 34.7% received chemotherapy (9,797/28,218) and 66.3% did not receive chemotherapy (18,421/28,218). Chemotherapy prescription failed to improve 10-year DFS (OR: 0.89, 95% CI: 0.65-1.23) and OS (OR: 0.92, 95% CI: 0.72-1.18). When using time-to-effect modelling, chemotherapy prescription failed to improve DFS (hazard ratio (HR): 1.01, 95% CI: 0.78-1.31) and OS (HR: 1.07, 95% CI: 0.89-1.27, I²= 67%).

CONCLUSION

This meta-analysis illustrates no long-term survival advantage associated with chemotherapy prescription in the setting of early-stage ILC. In the absence of well-designed, prospective clinical trials evaluating the impact of chemotherapy on long-term outcomes in ILC, these results should be considered by the multidisciplinary team when deciding on the value of systemic chemotherapy prescription in ILC.

CDH1 (E-cadherin) Gene Methylation in Human Breast Cancer: Critical Appraisal of a Long and Twisted Story

Simple Summary

Genes can be inactivated by specific modifications of DNA bases, most often by adding a methyl group to the DNA base cytosine if it is followed by guanosine (CG methylation). This modification prevents gene expression and has been reported for many different genes in nearly all types of cancer. A prominent example is the gene CDH1, which encodes the cell-adhesion molecule E-cadherin. This is an important player in the spreading of tumor cells within the body (metastasis). Particularly in human breast cancer, many different research groups have studied the inactivation of the CDH1 gene via DNA methylation using various methods. Over the last 20 years, different, in part, even contradicting results have been published for the CDH1 gene in breast cancer. This review summarizes the most important publications and explains the bewildering heterogeneity of results through careful analysis of the methods which have been used.

Abstract

Epigenetic inactivation of a tumor suppressor gene by aberrant DNA methylation is a well-established defect in human tumor cells, complementing genetic inactivation by mutation (germline or somatic). In human breast cancer, aberrant gene methylation has diagnostic, prognostic, and predictive potential. A prominent example is the hypermethylation of the CDH1 gene, encoding the adhesion protein E-Cadherin (“epithelial cadherin”). In numerous publications, it is reported as frequently affected by gene methylation in human breast cancer. However, over more than two decades of research, contradictory results concerning CDH1 gene methylation in human breast cancer accumulated. Therefore, we review the available evidence for and against the role of DNA methylation of the CDH1 gene in human breast cancer and discuss in detail the methodological reasons for conflicting results, which are of general importance for the analysis of aberrant DNA methylation in human cancer specimens. Since the loss of E-cadherin protein expression is a hallmark of invasive lobular breast cancer (ILBC), special attention is paid to CDH1 gene methylation as a potential mechanism for loss of expression in this special subtype of human breast cancer. Proper understanding of the methodological basis is of utmost importance for the correct interpretation of results supposed to demonstrate the presence and clinical relevance of aberrant DNA methylation in cancer specimens.

Chromatin accessibility landscape and active transcription factors in primary human invasive lobular and ductal breast carcinomas

BACKGROUND

Invasive lobular breast carcinoma (ILC), the second most prevalent histological subtype of breast cancer, exhibits unique molecular features compared with the more common invasive ductal carcinoma (IDC). While genomic and transcriptomic features of ILC and IDC have been characterized, genome-wide chromatin accessibility pattern differences between ILC and IDC remain largely unexplored.

METHODS

Here, we characterized tumor-intrinsic chromatin accessibility differences between ILC and IDC using primary tumors from The Cancer Genome Atlas (TCGA) breast cancer assay for transposase-accessible chromatin with sequencing (ATAC-seq) dataset.

RESULTS

We identified distinct patterns of genome-wide chromatin accessibility in ILC and IDC. Inferred patient-specific transcription factor (TF) motif activities revealed regulatory differences between and within ILC and IDC tumors. EGR1, RUNX3, TP63, STAT6, SOX family, and TEAD family TFs were higher in ILC, while ATF4, PBX3, SPDEF, PITX family, and FOX family TFs were higher in IDC.

CONCLUSIONS

This study reveals the distinct epigenomic features of ILC and IDC and the active TFs driving cancer progression that may provide valuable information on patient prognosis.

Results of a worldwide survey on the currently used histopathological diagnostic criteria for invasive lobular breast cancer

Invasive lobular carcinoma (ILC) represents the second most common subtype of breast cancer (BC), accounting for up to 15% of all invasive BC. Loss of cell adhesion due to functional inactivation of E-cadherin is the hallmark of ILC. Although the current world health organization (WHO) classification for diagnosing ILC requires the recognition of the dispersed or linear non-cohesive growth pattern, it is not mandatory to demonstrate E-cadherin loss by immunohistochemistry (IHC). Recent results of central pathology review of two large randomized clinical trials have demonstrated relative overdiagnosis of ILC, as only ~60% of the locally diagnosed ILCs were confirmed by central pathology. To understand the possible underlying reasons of this discrepancy, we undertook a worldwide survey on the current practice of diagnosing BC as ILC. A survey was drafted by a panel of pathologists and researchers from the European lobular breast cancer consortium (ELBCC) using the online tool SurveyMonkey®. Various parameters such as indications for IHC staining, IHC clones, and IHC staining procedures were questioned. Finally, systematic reporting of non-classical ILC variants were also interrogated. This survey was sent out to pathologists worldwide and circulated from December 14, 2020 until July, 1 2021. The results demonstrate that approximately half of the institutions use E-cadherin expression loss by IHC as an ancillary test to diagnose ILC and that there is a great variability in immunostaining protocols. This might cause different staining results and discordant interpretations. As ILC-specific therapeutic and diagnostic avenues are currently explored in the context of clinical trials, it is of importance to improve standardization of histopathologic diagnosis of ILC diagnosis.