Multi-institutional Assessment of Pathologist Scoring HER2 Immunohistochemistry.

The HercepTest was approved 20+ years ago as the companion diagnostic test for trastuzumab in human epidermal growth factor 2 (HER2) or ERBB2 gene-amplified/overexpressing breast cancers. Subsequent HER2 immunohistochemistry (IHC) assays followed, including the now most common Ventana 4B5 assay. Although this IHC assay has become the clinical standard, its reliability, reproducibility, and accuracy have largely been approved and accepted on the basis of concordance among small numbers of pathologists without validation in a real-world setting. In this study, we evaluated the concordance and interrater reliability of scoring HER2 IHC in 170 breast cancer biopsies by 18 breast cancer-specialized pathologists from 15 institutions. We used the Observers Needed to Evaluate Subjective Tests method to determine the plateau of concordance and the minimum number of pathologists needed to estimate interrater agreement values for large numbers of raters, as seen in the real-world setting. We report substantial discordance within the intermediate categories (<1% agreement for 1+ and 3.6% agreement for 2+) in the 4-category HER2 IHC scoring system. The discordance within the IHC 0 cases is also substantial with an overall percent agreement (OPA) of only 25% and poor interrater reliability metrics (0.49 Fleiss' kappa, 0.55 intraclass correlation coefficient). This discordance can be partially reduced by using a 3-category system (28.8% vs 46.5% OPA for 4-category and 3-category scoring systems, respectively). Observers Needed to Evaluate Subjective Tests plots suggest that the OPA for the task of determining a HER2 IHC score 0 from not 0 plateaus statistically around 59.4% at 10 raters. Conversely, at the task of scoring HER2 IHC as 3+ or not 3+ pathologists' concordance was much higher with an OPA that plateaus at 87.1% with 6 raters. This suggests that legacy HER2 IHC remains valuable for finding the patients in whom the ERBB2 gene is amplified but unacceptably discordant in assigning HER2-low or HER2-negative status for the emerging HER2-low therapies.

PD-L1 protein expression in relation to recurrence score values in early-stage ER + breast cancer.

PURPOSE: We assessed associations between PD-L1 protein expression, RS, tumor grade, and stromal tumor-infiltrating lymphocyte (TIL) count in early-stage ER + cancers. METHODS: FFPE tissue blocks of 213 patients with RS in 2012-2017 were identified. PD-L1 immunohistochemistry was performed with SP142 assay, cases with ≥ 1% tumor-infiltrating immune cell positivity in the tumor area were considered PD-L1 + . TIL scores were determined following the international TIL counting guidelines. PD-L1 expression positivity rates were compared across RS (< 11, 11-25, > 25) and TIL categories (< 10%, 10-29%, > 30%), and tumor grade using Wilcoxon and Chi-square tests. Multivariate analysis was performed using logistic regression. RESULTS: PD-L1 and TIL results were available for 201 and 203 patients. Overall, 53% of cases were PD-L1 +. PD-L1 expression was higher among cases with RS > 25, versus RS < 11 (p = 0.00019) and RS 11-25 (p = 0.0017). PD-L1 positivity also correlated with TIL score, tumor grade, and tumor size. Among cancers with TIL > 30%, 92% were PD-L1 + versus 44% PD-L1 + among TIL < 10% (p = 2.8 × 10-6). Grade 3 cancers had higher PD-L1 positivity (79% PD-L1 +) versus grade 2 (49% PD-L1 +) or 1 tumors (48% PD-L1 +) (p = 0.00047). T2 and T3 tumors had more frequent PD-L1 positivity (67% and 83%, respectively) versus T1 cancers (46%) (p = 0.008). In multivariate analysis, only TIL and RS remained as independent predictors of PD-L1 positivity. CONCLUSION: PD-L1 expression is significantly more frequent and higher in larger tumors (T2, T3), grade 3 cancers, and in cancers with RS > 25. PD-L1 expression also correlates with TIL score.

Standardizing Pathologic Evaluation of Breast Carcinoma After Neoadjuvant Chemotherapy.

CONTEXT.­: Neoadjuvant systemic therapy refers to the use of systemic agent(s) for malignancy prior to surgical treatment and has recently emerged as an option for most breast cancer patients eligible for adjuvant systemic therapy. Consequently, treated breast carcinomas have become routine specimens in pathology practices. A standard protocol has not yet been universally adopted for the evaluation and reporting of these specimens. The American Joint Committee on Cancer staging system recognizes the challenges in staging breast carcinomas after neoadjuvant treatment and provides important data points but does not currently provide detailed guidance in estimating the residual tumor burden in the breast and lymph nodes. The Residual Cancer Burden system is the only Web-based system that quantifies treatment response as a continuous variable using residual tumor burden in the breast and the lymph nodes. OBJECTIVE.­: To provide clarifications and guidance for evaluation and reporting of postneoadjuvant breast specimens, discuss issues with the current staging and reporting systems, and provide specific suggestions for future modifications to the American Joint Committee on Cancer system and the Residual Cancer Burden calculator. DATA SOURCES.­: English-language literature on the subject and the data from the I-SPY 2, a multicenter, adaptive randomization phase 2 neoadjuvant platform trial for early-stage, high-risk breast cancer patients. CONCLUSIONS.­: This article highlights challenges in the pathologic evaluation and reporting of treated breast carcinomas and provides recommendations and clarifications for pathologists and clinicians. It also provides specific recommendations for staging and discusses future directions.

Tumor immune microenvironment of self-identified African American and non-African American triple negative breast cancer.

Differences in the tumor immune microenvironment may result in differences in prognosis and response to treatment in cancer patients. We hypothesized that differences in the tumor immune microenvironment may exist between African American (AA) and NonAA patients, due to ancestry-related or socioeconomic factors, that may partially explain differences in clinical outcomes. We analyzed clinically matched triple-negative breast cancer (TNBC) tissues from self-identified AA and NonAA patients and found that stromal TILs, PD-L1 IHC-positivity, mRNA expression of immune-related pathways, and immunotherapy response predictive signatures were significantly higher in AA samples (p < 0.05; Fisher's Exact Test, Mann-Whitney Test, Permutation Test). Cancer biology and metabolism pathways, TAM-M2, and Immune Exclusion were significantly higher in NonAA samples (p < 0.05; Permutation Test, Mann-Whitney Test). There were no differences in somatic tumor mutation burden. Overall, there is greater immune infiltration and inflammation in AA TNBC and these differences may impact response to immune checkpoint inhibitors and other therapeutic agents that modulate the immune microenvironment.

Clinical Outcomes and Immune Markers by Race in a Phase I/II Clinical Trial of Durvalumab Concomitant with Neoadjuvant Chemotherapy in Early-Stage TNBC.

PURPOSE: The incidence of triple-negative breast cancer (TNBC) is higher among Black or African American (AA) women, yet they are underrepresented in clinical trials. To evaluate safety and efficacy of durvalumab concurrent with neoadjuvant chemotherapy for stage I-III TNBC by race, we enrolled additional AA patients to a Phase I/II clinical trial. PATIENTS AND METHODS: Our study population included 67 patients. The primary efficacy endpoint was pathologic complete response (pCR; ypT0/is, N0) rate. χ2 tests were used to evaluate associations between race and baseline characteristics. Cox proportional hazards models were used to assess association between race and overall survival (OS) and event-free survival (EFS). Multivariate logistic regression analyses were used to evaluate associations between race and pCR, immune-related adverse events (irAE) and recurrence. RESULTS: Twenty-one patients (31%) self-identified as AA. No significant associations between race and baseline tumor stage (P = 0.40), PD-L1 status (0.92), and stromal tumor-infiltrating lymphocyte (sTIL) count (P = 0.57) were observed. pCR rates were similar between AA (43%) and non-AA patients (48%; P = 0.71). Three-year EFS rates were 78.3% and 71.4% in non-AA and AA patients, respectively [HR, 1.451; 95% confidence interval (CI), 0.524-4.017; P = 0.474]; 3-year OS was 87% and 81%, respectively (HR, 1.72; 95% CI, 0.481-6.136; P = 0.405). The incidence of irAEs was similar between AA and non-AA patients and no significant associations were found between irAEs and pathologic response. CONCLUSIONS: pCR rates, 3-year OS and EFS after neoadjuvant immunotherapy and chemotherapy were similar in AA and non-AA patients. Toxicities, including the frequency of irAEs, were also similar.

Predictive Markers of Response to Neoadjuvant Durvalumab with Nab-Paclitaxel and Dose-Dense Doxorubicin/Cyclophosphamide in Basal-Like Triple-Negative Breast Cancer.

PURPOSE: We examined gene expression, germline variant, and somatic mutation features associated with pathologic response to neoadjuvant durvalumab plus chemotherapy in basal-like triple-negative breast cancer (bTNBC). EXPERIMENTAL DESIGN: Germline and somatic whole-exome DNA and RNA sequencing, programmed death ligand 1 (PD-L1) IHC, and stromal tumor-infiltrating lymphocyte scoring were performed on 57 patients. We validated our results using 162 patients from the GeparNuevo randomized trial. RESULTS: Gene set enrichment analysis showed that pathways involved in immunity (adaptive, humoral, innate), JAK-STAT signaling, cancer drivers, cell cycle, apoptosis, and DNA repair were enriched in cases with pathologic complete response (pCR), whereas epithelial-mesenchymal transition, extracellular matrix, and TGFß pathways were enriched in cases with residual disease (RD). Immune-rich bTNBC with RD was enriched in CCL-3, -4, -5, -8, -23, CXCL-1, -3, -6, -10, and IL1, -23, -27, -34, and had higher expression of macrophage markers compared with immune-rich cancers with pCR that were enriched in IFNγ, IL2, -12, -21, chemokines CXCL-9, -13, CXCR5, and activated T- and B-cell markers (GZMB, CD79A). In the validation cohort, an immune-rich five-gene signature showed higher expression in pCR cases in the durvalumab arm (P = 0.040) but not in the placebo arm (P = 0.923) or in immune-poor cancers. Independent of immune markers, tumor mutation burden was higher, and PI3K, DNA damage repair, MAPK, and WNT/ß-catenin signaling pathways were enriched in germline and somatic mutations in cases with pCR. CONCLUSIONS: The TGFß pathway is associated with immune-poor phenotype and RD in bTNBC. Among immune-rich bTNBC RD, macrophage/neutrophil chemoattractants dominate the cytokine milieu, and IFNγ and activated B cells and T cells dominate immune-rich cancers with pCR.

Examination of Low ERBB2 Protein Expression in Breast Cancer Tissue.

IMPORTANCE: Trastuzumab deruxtecan (T-DXd) has shown efficacy in patients with breast cancer with ERBB2 immunohistochemistry (IHC) scores of 1+ or 2+ but not 0 as read in central pathology laboratories. The drug is currently being tested in large randomized clinical trials with registration intent for this patient population. OBJECTIVE: To determine the suitability of the current standard ERBB2 IHC assays to select patients with low ERBB2 positivity for treatment with T-DXd. DESIGN AND SETTING: Assessment of data from College of American Pathologists surveys and assessment of analytic data from a Yale University-based study of concordance of 18 pathologists reading 170 breast cancer biopsies. RESULTS: The total survey data set included scores over 2 years from 1391 to 1452 laboratories of 40 ERBB2 cores from each laboratory (20 cores twice a year for a total of 80). College of American Pathologists surveys show that 19% of cases read by the laboratories generate results with less than or equal to 70% concordance for IHC ERBB2 score 0 vs 1+. When 18 pathologists read the scanned slides from a selected set of breast cancer biopsies using a 4-point scale, there was only 26% concordance between 0 and 1+ compared with 58% concordance between 2+ and 3+. CONCLUSIONS AND RELEVANCE: In this study using a current standard ERBB2 IHC assay, the scoring accuracy for ERBB2 IHC in the low range (0 and 1+) was poor. This inaccuracy in the real world could lead to misassignment of many patients for treatment with T-DXd.

Deep learning trained on hematoxylin and eosin tumor region of Interest predicts HER2 status and trastuzumab treatment response in HER2+ breast cancer.

The current standard of care for many patients with HER2-positive breast cancer is neoadjuvant chemotherapy in combination with anti-HER2 agents, based on HER2 amplification as detected by in situ hybridization (ISH) or protein immunohistochemistry (IHC). However, hematoxylin & eosin (H&E) tumor stains are more commonly available, and accurate prediction of HER2 status and anti-HER2 treatment response from H&E would reduce costs and increase the speed of treatment selection. Computational algorithms for H&E have been effective in predicting a variety of cancer features and clinical outcomes, including moderate success in predicting HER2 status. In this work, we present a novel convolutional neural network (CNN) approach able to predict HER2 status with increased accuracy over prior methods. We trained a CNN classifier on 188 H&E whole slide images (WSIs) manually annotated for tumor Regions of interest (ROIs) by our pathology team. Our classifier achieved an area under the curve (AUC) of 0.90 in cross-validation of slide-level HER2 status and 0.81 on an independent TCGA test set. Within slides, we observed strong agreement between pathologist annotated ROIs and blinded computational predictions of tumor regions / HER2 status. Moreover, we trained our classifier on pre-treatment samples from 187 HER2+ patients that subsequently received trastuzumab therapy. Our classifier achieved an AUC of 0.80 in a five-fold cross validation. Our work provides an H&E-based algorithm that can predict HER2 status and trastuzumab response in breast cancer at an accuracy that may benefit clinical evaluations.

Determination of the number of observers needed to evaluate a subjective test and its application in two PD-L1 studies.

In pathological studies, subjective assays, especially companion diagnostic tests, can dramatically affect treatment of cancer. Binary diagnostic test results (ie, positive vs negative) may vary between pathologists or observers who read the tumor slides. Some tests have clearly defined criteria resulting in highly concordant outcomes, even with minimal training. Other tests are more challenging. Observers may achieve poor concordance even with training. While there are many statistically rigorous methods for measuring concordance between observers, we are unaware of a method that can identify how many observers are needed to determine whether a test can reach an acceptable concordance, if at all. Here we introduce a statistical approach to the assessment of test performance when the test is read by multiple observers, as would occur in the real world. By plotting the number of observers against the estimated overall agreement proportion, we can obtain a curve that plateaus to the average observer concordance. Diagnostic tests that are well-defined and easily judged show high concordance and plateau with few interobserver comparisons. More challenging tests do not plateau until many interobserver comparisons are made, and typically reach a lower plateau or even 0. We further propose a statistical test of whether the overall agreement proportion will drop to 0 with a large number of pathologists. The proposed analytical framework can be used to evaluate the difficulty in the interpretation of pathological test criteria and platforms, and to determine how pathology-based subjective tests will perform in the real world. The method could also be used outside of pathology, where concordance of a diagnosis or decision point relies on the subjective application of multiple criteria. We apply this method in two recent PD-L1 studies to test whether the curve of overall agreement proportion will converge to 0 and determine the minimal sufficient number of observers required to estimate the concordance plateau of their reads.

A Novel Immunomodulatory 27-Gene Signature to Predict Response to Neoadjuvant Immunochemotherapy for Primary Triple-Negative Breast Cancer.

A precise predictive biomarker for TNBC response to immunochemotherapy is urgently needed. We previously established a 27-gene IO signature for TNBC derived from a previously established 101-gene model for classifying TNBC. Here we report a pilot study to assess the performance of a 27-gene IO signature in predicting the pCR of TNBC to preoperative immunochemotherapy. We obtained RNA sequencing data from the primary tumors of 55 patients with TNBC, who received neoadjuvant immunochemotherapy with the PD-L1 blocker durvalumab. We determined the power and accuracy in predicting pCR for the immunomodulatory (IM) subtype identified by the 101-gene model, the 27-gene IO signature, and PD-L1 expression by immunohistochemistry (IHC). The pCR rate was 45% (25/55). The odds ratios for pCR were as follows: IM subtype by 101-gene model, 3.14 (p = 0.054); 27-gene IO signature, 4.13 (p = 0.012); PD-L1 expression by IHC, 2.63 (p = 0.106); 27-gene IO signature in combination with PD-L1 expression by IHC, 6.53 (p = 0.003). The 27-gene IO signature has the potential to predict the pCR of primary TNBC to neoadjuvant immunochemotherapy. Further analysis in a large cohort is needed.

Interobserver variability in the assessment of stromal tumor-infiltrating lymphocytes (sTILs) in triple-negative invasive breast carcinoma influences the association with pathological complete response: the IVITA study.

High stromal tumor-infiltrating lymphocytes (sTILs) in triple-negative breast cancer (TNBC) are associated with pathological complete response (pCR) after neoadjuvant chemotherapy (NAC). Histopathological assessment of sTILs in TNBC biopsies is characterized by substantial interobserver variability, but it is unknown whether this affects its association with pCR. Here, we aimed to investigate the degree of interobserver variability in an international study, and its impact on the relationship between sTILs and pCR. Forty pathologists assessed sTILs as a percentage in digitalized biopsy slides, originating from 41 TNBC patients who were treated with NAC followed by surgery. Pathological response was quantified by the MD Anderson Residual Cancer Burden (RCB) score. Intraclass correlation coefficients (ICCs) were calculated per pathologist duo and Bland-Altman plots were constructed. The relation between sTILs and pCR or RCB class was investigated. The ICCs ranged from -0.376 to 0.947 (mean: 0.659), indicating substantial interobserver variability. Nevertheless, high sTILs scores were significantly associated with pCR for 36 participants (90%), and with RCB class for eight participants (20%). Post hoc sTILs cutoffs at 20% and 40% resulted in variable associations with pCR. The sTILs in TNBC with RCB-II and RCB-III were intermediate to those of RCB-0 and RCB-I, with lowest sTILs observed in RCB-I. However, the limited number of RCB-I cases precludes any definite conclusions due to lack of power, and this observation therefore requires further investigation. In conclusion, sTILs are a robust marker for pCR at the group level. However, if sTILs are to be used to guide the NAC scheme for individual patients, the observed interobserver variability might substantially affect the chance of obtaining a pCR. Future studies should determine the 'ideal' sTILs threshold, and attempt to fine-tune the patient selection for sTILs-based de-escalation of NAC regimens. At present, there is insufficient evidence for robust and reproducible sTILs-guided therapeutic decisions.

HER-2/neu-positive breast cancer neoadjuvant chemotherapy response after implementation of 2018 ASCO/CAP focused update.

Human Epidermal Growth Factor Receptor 2 (HER2), a routinely tested breast cancer marker, is associated with worse prognosis yet increased sensitivity to targeted neoadjuvant therapy (NAT) in breast cancer patients. The presence of HER2 in breast carcinoma can be detected with either immunohistochemistry (IHC) or in situ hybridization (ISH). In this study, we examine the relationship between clinicopathological features, HER2 detection method (IHC vs ISH), and prognostic outcomes in NAT-treated HER2-positive breast cancer patients. We included 99 HER2-positive patients from three academic institutions following 2018 HER2 testing updates and conducted a retrospective correlational study. Seventy-one (72%) were HER2-positive by IHC and 28 (28%) were positive following reflexive ISH. Multivariate analysis showed biomarker status to be significantly associated with pathologic complete response (pCR) (p = 0.003), Residual Cancer Burden (RCB) (p = 0.007), and tumor size downstaging (p = 0.002) and HER2 detection method of IHC to be significantly associated with pCR (p = 0.05), RCB (p = 0.004), and nodal downstaging (p= 0.03). In conclusion, HER2 detection method and biomarker subtype allow for further prognostic stratification of HER2-positive patients when 2018 American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guideline updates are applied.

Characteristics and Long-Term Risk of Breast Angiosarcoma.

BACKGROUND: Angiosarcoma of the breast is rare and aggressive. It can occur as a de novo tumor or secondary to breast cancer treatment. The purpose of this study is to analyze differences between patients with primary and secondary angiosarcoma of the breast and investigate potential risk factors for its development. PATIENTS AND METHODS: The Surveillance, Epidemiology, and End Results program of the National Cancer Institute database was queried to identify patients with angiosarcoma of the breast, trunk, shoulder, and upper arm. The population-based incidence was analyzed. Primary and secondary angiosarcoma cases were identified and compared. Breast cancer characteristics of secondary angiosarcoma patients were compared with all breast cancer patients in the database who did not develop angiosarcoma. RESULTS: Overall, 904 patients were included, and 65.4% were secondary angiosarcomas. These patients had worse survival, were older, more likely to be White, more likely to have regionally advanced disease, and had angiosarcoma tumors of higher pathologic grade. Independent factors associated with development of secondary angiosarcoma among breast cancer patients included White race, older age, invasive tumor, lymph node removal, lumpectomy, radiation treatment, and left-sided tumor. Although the mean time to develop angiosarcoma after breast cancer diagnosis was 8.2 years, the risk continues to increase up to 30 years after breast cancer treatment. CONCLUSION: Angiosarcoma is rare but increasing in incidence. Secondary angiosarcomas are more common and exhibit more aggressive behavior. Several factors for angiosarcoma after breast cancer treatment could be identified, which may help us counsel and identify patients at risk.

Neoadjuvant durvalumab plus weekly nab-paclitaxel and dose-dense doxorubicin/cyclophosphamide in triple-negative breast cancer.

The goal of this Phase I/II trial is to assess the safety and efficacy of administering durvalumab concurrent with weekly nab-paclitaxel and dose-dense doxorubicin/cyclophosphamide (ddAC) neoadjuvant therapy for stages I-III triple-negative breast cancer. The primary endpoint is pathologic complete response (pCR:ypT0/is, ypN0). The response was correlated with PDL1 expression and stromal tumor-infiltrating lymphocytes (sTILs). Two dose levels of durvalumab (3 and 10 mg/kg) were assessed. PD-L1 was assessed using the SP263 antibody; ≥1% immune and tumor cell staining was considered positive; sTILs were calculated as the area occupied by mononuclear inflammatory cells over the total intratumoral stromal area. 59 patients were evaluable for toxicity and 55 for efficacy in the Phase II study (10 mg/kg dose). No dose-limiting toxicities were observed in Phase I. In Phase II, pCR rate was 44% (95% CI: 30-57%); 18 patients (31%) experienced grade 3/4 treatment-related adverse events (AE), most frequently neutropenia (n = 4) and anemia (n = 4). Immune-related grade 3/4 AEs included Guillain-Barre syndrome (n = 1), colitis (n = 2), and hyperglycemia (n = 2). Of the 50 evaluable patients for PD-L1, 31 (62%) were PD-L1 positive. pCR rates were 55% (95% CI: 0.38-0.71) and 32% (95% CI: 0.12-0.56) in the PD-L1 positive and negative groups (p = 0.15), respectively. sTIL counts were available on 52 patients and were significantly higher in the pCR group (p = 0.0167). Concomitant administration of durvalumab with sequential weekly nab-paclitaxel and ddAC neoadjuvant chemotherapy resulted in a pCR rate of 44%; pCR rates were higher in sTIL-high cancers.

LMNA-NTRK1 rearranged mesenchymal tumor (lipofibromatosis-like neural tumor) mimicking pigmented dermatofibrosarcoma protuberans.

We present the case of a 31-year-old female with a 1.5 cm pigmented nodule on the scalp. Histopathological examination revealed a proliferation of relatively bland spindle cells and pigmented dendritic cells, with interspersed lymphoid follicles diffusely infiltrating the adipose tissue. The microscopic differential diagnosis included pigmented dermatofibrosarcoma protuberans (DFSP). The spindle cells showed S-100 and CD34 labeling but were negative for SOX-10. Immunohistochemical stain for pan-TRK was positive, while fluorescence in-situ hybridization for PDGFB gene rearrangement was negative. Targeted RNA sequencing revealed an LMNA-NTRK1 (exon2/exon10) fusion. This molecular result coupled with the histopathological findings and immunohistochemical profile supported the diagnosis of the recently characterized NTRK-rearranged spindle cell neoplasm termed "lipofibromatosis-like neural tumor (LPF-NT)." These neoplasms typically occur in superficial soft tissue and are characterized by a distinctive immunoprofile (CD34+, S-100+, SOX10-). Histopathological differential diagnosis for LPF-NT tumors includes lipofibromatosis, DFSP, low-grade malignant peripheral nerve sheath tumor, and spindle cell/desmoplastic melanoma. The pigmented dendritic cells reminiscent of pigmented DFSP and lymphoid follicles noted in our case have not been previously reported in LPF-NT, thus expanding the morphological spectrum of this entity. LMNA-NTRK1 fusion serves both as a diagnostic and therapeutic biomarker, as cases with advanced disease may be amenable to targeted therapy using tyrosine kinase inhibitors.

Stromal Changes are Associated with High P4HA2 Expression in Ductal Carcinoma in Situ of the Breast.

Ductal carcinoma in situ (DCIS) of the breast is able to induce stromal changes, which likely reflect the crosstalk between DCIS and its microenvironment. These changes harbor prognostic information, although the interobserver variability of scoring stromal changes is moderate. A more robust evaluation of the DCIS-associated stroma is therefore needed. The aim of this study was to characterize P4HA2 expression, which is involved in collagen biosynthesis, in DCIS and to assess whether P4HA2 expression enables a more robust evaluation of the DCIS-associated stroma compared to histomorphology. This study included 410 patients with DCIS. Stromal changes were scored on hematoxylin/eosin-stained whole slides. P4HA2 expression in DCIS-associated stroma was assessed by whole slide immunohistochemistry. One hundred DCIS lesions were evaluated by seven pathologists to study the interobserver variability in the assessment of stromal changes and stromal P4HA2 expression. High P4HA2 expression in stromal fibroblasts was present in 14.1% of the patients. High P4HA2 expression was associated with the presence of periductal stromal changes (P = 0.004). The interobserver variability was similar for the assessment of stromal changes and the percentage of P4HA2-positive fibroblasts. Although we demonstrated a significant association between high P4HA2 expression in fibroblasts and the morphological presence of stromal changes, it seems unlikely that P4HA2 expression can be used as an alternative for the histopathological evaluation of the DCIS-associated stroma.

Expression of lymphoid enhancer-binding factor 1 in breast fibroepithelial lesions.

Phyllodes tumors (PTs) are rare epithelial-mesenchymal tumors of the breast with malignant potential. Here, we evaluate the nuclear expression of lymphoid enhancer-binding factor 1 (LEF-1), a transcription factor downstream of Wnt/ß-catenin signaling, in fibroepithelial lesions of the breast. Excised fibroepithelial lesions of the breast were retrospectively reviewed, blinded to the original diagnosis, and classified according to World Health Organization (WHO) criteria. A tissue microarray (TMA) was composed with two representative cores from each case, including 24 benign lesions, 11 borderline phyllodes, and 8 malignant PTs. ß-Catenin, LEF-1, p120, and E-cadherin immunohistochemistry was performed on the TMA, and staining was quantified. The malignant/borderline PTs showed higher stromal LEF-1 expression than benign tumors (P < 0.001). Stromal cells expressed LEF-1 in 100% (16/16 of core TMA) of malignant phyllodes, compared with 73% (16/22) borderline and 27% (13/48) benign tumors. The average LEF-1 H-score was 24.9, 6.1, and 1.5 for malignant, borderline, and benign tumors, respectively. Nuclear expression of ß-catenin in the stromal component was more often seen in malignant than in borderline and benign tumors (44% versus 32% and 23%, respectively). Nine TMA cores of malignant tumors without nuclear ß-catenin staining demonstrated LEF-1 expression. Both LEF-1 and nuclear ß-catenin showed expression in the majority of borderline/malignant PTs suggesting a biological progression of Wnt/ß-catenin pathway activation in the stromal component from benign to malignant tumors. Inhibitors for the Wnt/ß-catenin pathway may provide alternative treatment options in the future for malignant or metastatic PTs.

Prospective multi-institutional evaluation of pathologist assessment of PD-L1 assays for patient selection in triple negative breast cancer.

The US Food and Drug Administration (FDA) approved the PD-L1 immunohistochemical assay, SP142, as a companion test to determine eligibility for atezolizumab therapy in patients with advanced triple negative breast cancer (TNBC) but data in lung cancer studies suggest the assay suffers from poor reproducibility. We sought to evaluate reproducibility and concordance in PD-L1 scoring across multiple pathologists. Full TNBC sections were stained with SP142 and SP263 assays and interpreted for percentage (%) immune cell (IC) staining by 19 pathologists from 14 academic institutions. Proportion of PD-L1 positive cases (defined as ≥1% IC) was determined for each assay as well as concordance across observers. We utilized a new method we call Observers Needed to Evaluate Subjective Tests (ONEST) to determine the minimum number of evaluators needed to estimate concordance between large numbers of readers, as occurs in the real-world setting. PD-L1 was interpreted as positive with the SP142 assay in an average 58% of cases compared with 78% with SP263 (p < 0.0001). IC positive continuous scores ranged from 1 to 95% (mean = 20%) and 1 to 90% (mean = 10%) for SP263 and SP142, respectively. With SP142, 26 cases (38%) showed complete two category (<1% vs. ≥1%) concordance; with SP263, 38 cases (50%) showed complete agreement. The intraclass correlation coefficient (ICC) for two category scoring of SP263 and SP142 was 0.513 and 0.560. ONEST plots showed decreasing overall percent agreement (OPA) as observer number increased, reaching a low plateau of 0.46 at ten observers for SP263 and 0.41 at eight observers for SP142. IC scoring with both assays showed poor reproducibility across multiple pathologists with ONEST analysis suggesting more than half of pathologists will disagree about IC scores. This could lead to many patients either receiving atezolizumab when they are unlikely to benefit, or not receiving atezolizumab when they may benefit.

Reciprocal expression of Annexin A6 and RasGRF2 discriminates rapidly growing from invasive triple negative breast cancer subsets.

Actively growing tumors are often histologically associated with Ki67 positivity, while the detection of invasiveness relies on non-quantitative pathologic evaluation of mostly advanced tumors. We recently reported that reduced expression of the Ca2+-dependent membrane-binding annexin A6 (AnxA6) is associated with increased expression of the Ca2+ activated RasGRF2 (GRF2), and that the expression status of these proteins inversely influence the growth and motility of triple negative breast cancer (TNBC) cells. Here, we establish that the reciprocal expression of AnxA6 and GRF2 is at least in part, dependent on inhibition of non-selective Ca2+ channels in AnxA6-low but not AnxA6-high TNBC cells. Immunohistochemical staining of breast cancer tissues revealed that compared to non-TNBC tumors, TNBC tumors express lower levels of AnxA6 and higher Ki67 expression. GRF2 expression levels strongly correlated with high Ki67 in pretreatment biopsies from patients with residual disease and with residual tumor size following chemotherapy. Elevated AnxA6 expression more reliably identified patients who responded to chemotherapy, while low AnxA6 levels were significantly associated with shorter distant relapse-free survival. Finally, the reciprocal expression of AnxA6 and GRF2 can delineate GRF2-low/AnxA6-high invasive from GRF2-high/AnxA6-low rapidly growing TNBCs. These data suggest that AnxA6 may be a reliable biomarker for distant relapse-free survival and response of TNBC patients to chemotherapy, and that the reciprocal expression of AnxA6 and GRF2 can reliably delineate TNBCs into rapidly growing and invasive subsets which may be more relevant for subset-specific therapeutic interventions.