Intratumor spatial heterogeneity in programmed death-ligand 1 (PD-L1) protein expression in early-stage breast cancer.

PURPOSE: Programmed death-ligand 1 (PD-L1) expression is required for benefit from immune checkpoint inhibitors in metastatic triple negative breast cancer (TNBC). In contrast, in the neoadjuvant setting patients benefited regardless of PD-L1 expression. We hypothesized that, in stages II-III breast cancers, low levels of PD-L1 expression may be sufficient to confer sensitivity to therapy and focal expression could be missed by a biopsy. METHODS: In this study, we examined intratumor spatial heterogeneity of PD-L1 protein expression in multiple biopsies from different regions of breast cancers in 57 primary breast tumors (n = 33 TNBC, n = 19 estrogen receptor-positive [ER-positive], n = 5 human epidermal receptor 2-positive [HER2 +]). E1L3N antibody was used to assess PD-L1 status and staining was scored using the combined positivity score (CPS) with PD-L1 positive defined as CPS ≥ 10. RESULTS: Overall, 19% (11/57) of tumors were PD-L1 positive based on positivity in at least 1 biopsy. Among TNBC, PD-L1 positivity was 27% (9/33). The discordance rate, defined as the same tumor yielding PD-L1 positive and negative samples in different regions, was 16% (n = 9) in the whole study population and 23% (n = 7) in TNBC. Cohen's kappa coefficient of agreement was 0.214 for the whole study and 0.239 for TNBC, both of which falling into a non-statistically significant fair agreement range. Among all PD-L1 positive cases, 82% (n = 9/11) had positivity in only one of the tissue assessments. CONCLUSION: These results indicate that the overall 84% concordance is driven by concordant negative results. In PD-L1 positive cancers, within-tumor heterogeneity in PD-L1 expression exists.

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.

Histologic grading of breast carcinoma: a multi-institution study of interobserver variation using virtual microscopy.

Breast carcinoma grading is an important prognostic feature recently incorporated into the AJCC Cancer Staging Manual. There is increased interest in applying virtual microscopy (VM) using digital whole slide imaging (WSI) more broadly. Little is known regarding concordance in grading using VM and how such variability might affect AJCC prognostic staging (PS). We evaluated interobserver variability amongst a multi-institutional group of breast pathologists using digital WSI and how discrepancies in grading would affect PS. A digitally scanned slide from 143 invasive carcinomas was independently reviewed by 6 pathologists and assigned grades based on established criteria for tubule formation (TF), nuclear pleomorphism (NP), and mitotic count (MC). Statistical analysis was performed. Interobserver agreement for grade was moderate (κ = 0.497). Agreement was fair (κ = 0.375), moderate (κ = 0.491), and good (κ = 0.705) for grades 2, 3, and 1, respectively. Observer pair concordance ranged from fair to good (κ = 0.354-0.684) Perfect agreement was observed in 43 cases (30%). Interobserver agreement for the individual components was best for TF (κ = 0.503) and worst for MC (κ = 0.281). Seventeen of 86 (19.8%) discrepant cases would have resulted in changes in PS and discrepancies most frequently resulted in a PS change from IA to IB (n = 9). For two of these nine cases, Oncotype DX results would have led to a PS of 1A regardless of grade. Using VM, a multi-institutional cohort of pathologists showed moderate concordance for breast cancer grading, similar to studies using light microscopy. Agreement was the best at the extremes of grade and for evaluation of TF. Whether the higher variability noted for MC is a consequence of VM grading warrants further investigation. Discordance in grading infrequently leads to clinically meaningful changes in the prognostic stage.

Apocrine Breast Cancer: Unique Features of a Predominantly Triple-Negative Breast Cancer.

INTRODUCTION: Invasive apocrine carcinoma is a rare breast cancer that is frequently triple negative. Little is known about the characteristics of its molecular subtypes. We compared the incidence, demographics, and clinicopathologic features of this cancer with non-apocrine carcinomas stratified by molecular subtype. METHODS: Women with invasive apocrine cancer were retrospectively identified from the Surveillance, Epidemiology, and End Results (SEER) database. Clinicopathologic and demographic features were compared with non-apocrine carcinomas, both overall using data from 2004 to 2017 and stratified by molecular subtypes using data from 2010 to 2017. The life table method was used to determine the 7-year breast cancer-specific survival. RESULTS: Compared with non-apocrine cancers, apocrine cancers presented at a younger age, with larger, higher-grade tumors that were much more likely to be triple negative (50% vs. 11%) or human epidermal growth factor receptor 2 (HER2)-positive (28% vs. 15%) and less likely to be luminal (22% vs. 74%); however, the 7-year survival was the same at 85%. The characteristics varied dramatically by molecular type. Compared with non-apocrine triple-negative, apocrine triple-negative patients were less likely to be African American and were much older, with smaller, lower-grade tumors and much better survival (86% vs. 74%). In contrast, compared with luminal non-apocrine, apocrine luminal patients had larger, higher-grade tumors and worse survival (79% vs. 89%). CONCLUSIONS: Invasive apocrine carcinomas have more aggressive features than non-apocrine carcinomas but the breast cancer-specific survival is the same. Half of these apocrine tumors are triple negative but these have more favorable features and much better survival than non-apocrine triple-negative cancers.

Discordant anti-SARS-CoV-2 spike protein and RNA staining in cutaneous perniotic lesions suggests endothelial deposition of cleaved spike protein.

BACKGROUND: Prior studies have shown the presence of immunohistochemical staining for the SARS-CoV-2 spike protein (SP) in endothelial cells and eccrine epithelium of acral perniosis classified as "COVID toes." Yet, other studies have been unable to detect SARS-CoV-2 RNA in skin biopsies of "COVID toes" by reverse-transcriptase polymerase chain reaction testing. OBJECTIVE: In order to address these apparently conflicting findings, we compared detection of SARS-CoV-2 SP, through RNA in situ hybridization (ISH) vs immunohistochemistry (IHC), in skin biopsies of acral perniotic lesions presenting during the COVID-19 pandemic. RESULTS: Three of six cases showed positive immunohistochemical labeling of endothelial cells, with one of three cases with sufficient depth also having labeling of eccrine glands, using an anti-SP SARS-CoV-2 antibody. These three cases positive with IHC were negative for SP by RNA ISH. CONCLUSION: While the gold standard for detection of SARS-CoV-2 in tissue sections has yet to be determined, the detection of SARS-CoV-2 SP alone without spike RNA suggests that cleaved SP may be present in cutaneous endothelial cells and eccrine epithelium, providing a potential pathogenetic mechanism of COVID-19 endotheliitis.

Perniosis during the COVID-19 pandemic: Negative anti-SARS-CoV-2 immunohistochemistry in six patients and comparison to perniosis before the emergence of SARS-CoV-2.

BACKGROUND: Acral inflammatory lesions that have some resemblance to idiopathic or autoimmune-associated perniosis (chilblains) have been described in multiple countries during the COVID-19 pandemic. METHODS: We examined histopathologic findings in six consecutive such cases from five patients received in mid-May to mid-June of 2020, evaluating immunohistochemical staining for the SARS-CoV-2 nucleocapsid protein. We compared these six cases to eight cases diagnosed as perniosis between January and June of 2019. RESULTS: Five of six lesions with perniosis-like histopathology during the COVID-19 pandemic had distinctive tight cuffing of lymphocytes; intravascular material was present in one case. SARS-CoV-2 immunohistochemical staining using an antibody directed at the nucleocapsid protein was negative in all six cases. Only one of eight specimens with microscopic findings of perniosis received prior to the COVID-19 pandemic had tightly cuffed perivascular lymphocytes, and none had obvious intravascular occlusion. CONCLUSIONS: A tightly cuffed pattern of perivascular lymphocytes is a feature of perniosis during the COVID-19 pandemic. The absence of SARS-CoV-2 nucleocapsid protein in these cases suggests against the virus being directly present in these lesions.

A Randomized, Controlled Trial of Cavity Shave Margins in Breast Cancer.

BACKGROUND: Routine resection of cavity shave margins (additional tissue circumferentially around the cavity left by partial mastectomy) may reduce the rates of positive margins (margins positive for tumor) and reexcision among patients undergoing partial mastectomy for breast cancer. METHODS: In this randomized, controlled trial, we assigned, in a 1:1 ratio, 235 patients with breast cancer of stage 0 to III who were undergoing partial mastectomy, with or without resection of selective margins, to have further cavity shave margins resected (shave group) or not to have further cavity shave margins resected (no-shave group). Randomization occurred intraoperatively after surgeons had completed standard partial mastectomy. Positive margins were defined as tumor touching the edge of the specimen that was removed in the case of invasive cancer and tumor that was within 1 mm of the edge of the specimen removed in the case of ductal carcinoma in situ. The rate of positive margins was the primary outcome measure; secondary outcome measures included cosmesis and the volume of tissue resected. RESULTS: The median age of the patients was 61 years (range, 33 to 94). On final pathological testing, 54 patients (23%) had invasive cancer, 45 (19%) had ductal carcinoma in situ, and 125 (53%) had both; 11 patients had no further disease. The median size of the tumor in the greatest diameter was 1.1 cm (range, 0 to 6.5) in patients with invasive carcinoma and 1.0 cm (range, 0 to 9.3) in patients with ductal carcinoma in situ. Groups were well matched at baseline with respect to demographic and clinicopathological characteristics. The rate of positive margins after partial mastectomy (before randomization) was similar in the shave group and the no-shave group (36% and 34%, respectively; P=0.69). After randomization, patients in the shave group had a significantly lower rate of positive margins than did those in the no-shave group (19% vs. 34%, P=0.01), as well as a lower rate of second surgery for margin clearance (10% vs. 21%, P=0.02). There was no significant difference in complications between the two groups. CONCLUSIONS: Cavity shaving halved the rates of positive margins and reexcision among patients with partial mastectomy. (Funded by the Yale Cancer Center; ClinicalTrials.gov number, NCT01452399.).

Loss of c-KIT expression in breast cancer correlates with malignant transformation of breast epithelium and is mediated by KIT gene promoter DNA hypermethylation.

KIT Proto-Oncogene Receptor Tyrosine Kinase (KIT) is a transmembrane receptor tyrosine kinase which plays an important role in regulation of cell proliferation, survival and migration. Interestingly, the role of c-KIT in malignant transformation seems to be highly tissue-specific and it can act either as an oncogene or tumor suppressor gene. Here we analyzed the expression of c-KIT in normal breast tissues and tissues from different stages encompassing major steps of breast tumor development. Our study showed, that the c-KIT protein expression is gradually lost during the process of breast tissue transformation. The analysis of previously published datasets revealed that c-KIT expression in breast malignancies was downregulated at mRNA level. Because sequencing studies did not identify any recurrent mutations or copy number alterations, we proposed a potential epigenetic mechanism for the downregulation of c-KIT expression. In-silico analysis of the KIT promoter revealed the presence of CpG islands, therefore we performed bisulfite sequencing of normal breast epithelial tissues as well as breast tumor samples. We found, that KIT promoter is hypermethylated in breast tumors compared to normal breast tissues. Furthermore, treatment of breast cancer cell lines, that lack the expression of c-KIT, with methyltransferase inhibitor 5-Azacytidine (5Aza-2dC) resulted in increased expression of c-KIT mRNA. Collectively, our studies demonstrate that c-KIT expression is epigenetically downregulated during breast epithelium transformation and cancer development via KIT promoter hypermethylation.

Breast cancer histopathology is predictive of low-risk Oncotype Dx recurrence score.

BACKGROUND: Oncotype Dx is a genetic test that has been incorporated into the 2017 AJCC breast cancer staging system for ER positive, HER2-negative, lymph node-negative patients to predict the risk of recurrence. Recent data suggest that immunohistochemistry (ER, PR, HER2, and Ki-67) and histologic subtype may identify patients that will not benefit from Oncotype Dx testing. METHODS: A total of 371 patients underwent Oncotype Dx testing at our institution from 2012 to 2016. Oncotype recurrence score was categorized as low- (ORS = 0-10), intermediate- (11-25), or high risk (26-100). Invasive carcinomas were categorized based on histologic subtype as "favorable" (mucinous, tubular, cribriform, tubulolobular, and lobular) and "unfavorable" (ductal, mixed ductal and lobular, and micropapillary carcinoma). All cases were estrogen receptor positive and HER2-negative. Clinical and histologic predictors of low-risk ORS were assessed in univariate and multivariate logistic regression. RESULTS: A total of 371 patients were categorized by ORS as low risk (n = 85, 22.9%), intermediate risk (n = 244, 65.8%), and high risk (n = 42, 11.3%). The histologic subtypes with the highest percentage of high-risk ORS were invasive micropapillary (n = 4/17, 23.5%), pleomorphic lobular (n = 2/10, 20%), and ductal carcinoma (n = 28/235, 11.9%). Low-grade invasive carcinomas with favorable histology rarely had a high-risk ORS (n = 1/97, 1%). In a simple multivariable model, favorable histologic subtype (OR = 2.39, 95% CI: 1.10 to 5.15, P = 0.026), and histologic grade (OR = 1.76, 95% CI: 1.07 to 2.90, P = 0.025) were the only significant predictors of an ORS less than 11 in estrogen receptor positive, HER2-negative, and lymph node-negative patients. CONCLUSION: We question the utility of performing Oncotype Dx in subtypes of invasive carcinoma that are associated with excellent prognosis. We propose that immunohistochemistry for ER, PR, and HER2 is sufficient for patients with low-grade invasive carcinomas and can be used as a surrogate for Oncotype Dx.

Economic Impact of Routine Cavity Margins Versus Standard Partial Mastectomy in Breast Cancer Patients: Results of a Randomized Controlled Trial.

OBJECTIVE: The aim of the study was to compare costs associated with excision of routine cavity shave margins (CSM) versus standard partial mastectomy (PM) in patients with breast cancer. BACKGROUND: Excision of CSM reduces re-excision rates by more than 50%. The economic implications of this is, however, unclear. METHODS: Between October 21, 2011 and November 25, 2013, 235 women undergoing PM for Stage 0-III breast cancer were randomized to undergo either standard PM ("no shave", n = 116) or have additional CSM taken ("shave", n = 119). Costs from both a payer and a hospital perspective were measured for index surgery and breast cancer surgery-related care through subsequent 90 days. RESULTS: The 2 groups were well-matched in terms of baseline characteristics. Those in the "shave" group had a longer operative time at the initial surgery (median 76 vs 66 min, P < 0.01), but a lower re-excision rate for positive margins (13/119 = 10.9% vs 32/116 = 27.6%, P < 0.01). Actual direct hospital costs associated with operating room time ($1315 vs. $1137, P = 0.03) and pathology costs ($1195 vs $795, P < 0.01) were greater for the initial surgery in patients in the "shave" group. Taking into account the index surgery and the subsequent 90 days, there was no significant difference in cost from either the payer ($10,476 vs $11,219, P = 0.40) or hospital perspective ($5090 vs $5116, P = 0.37) between the "shave" and "no shave" groups. CONCLUSIONS: Overall costs were not significantly different between the "shave" and "no shave" groups due to significantly fewer reoperative surgeries in the former.

Automated measurement of estrogen receptor in breast cancer: a comparison of fluorescent and chromogenic methods of measurement.

Whereas FDA-approved methods of assessment of estrogen receptor (ER) are 'fit for purpose', they represent a 30-year-old technology. New quantitative methods, both chromogenic and fluorescent, have been developed and studies have shown that these methods increase the accuracy of assessment of ER. Here, we compare three methods of ER detection and assessment on two retrospective tissue microarray (TMA) cohorts of breast cancer patients: estimates of percent nuclei positive by pathologists and by Aperio's nuclear algorithm (standard chromogenic immunostaining), and immunofluorescence as quantified with the automated quantitative analysis (AQUA) method of quantitative immunofluorescence (QIF). Reproducibility was excellent (R(2)>0.95) between users for both automated analysis methods, and the Aperio and QIF scoring results were also highly correlated, despite the different detection systems. The subjective readings show lower levels of reproducibility and a discontinuous, bimodal distribution of scores not seen by either mechanized method. Kaplan-Meier analysis of 10-year disease-free survival was significant for each method (Pathologist, P=0.0019; Aperio, P=0.0053, AQUA, P=0.0026); however, there were discrepancies in patient classification in 19 out of 233 cases analyzed. Out of these, 11 were visually positive by both chromogenic and fluorescent detection. In 10 cases, the Aperio nuclear algorithm labeled the nuclei as negative; in 1 case, the AQUA score was just under the cutoff for positivity (determined by an Index TMA). In contrast, 8 out of 19 discrepant cases had clear nuclear positivity by fluorescence that was unable to be visualized by chromogenic detection, perhaps because of low positivity masked by the hematoxylin counterstain. These results demonstrate that automated systems enable objective, precise quantification of ER. Furthermore, immunofluorescence detection offers the additional advantage of a signal that cannot be masked by a counterstaining agent. These data support the usage of automated methods for measurement of this and other biomarkers that may be used in companion diagnostic tests.

Fibroepithelial Neoplasm with Hybrid Features of Benign Phyllodes Tumor, Juvenile Papillomatosis, and Juvenile Fibroadenoma: A Case Report.

Phyllodes tumor is an uncommon breast fibroepithelial neoplasm mainly found in middle-aged patients, presenting a morphologic continuum from benign to malignant. Juvenile papillomatosis represents a rare benign proliferative breast tumor primarily affecting young individuals and carries a potential elevated risk of subsequent breast cancer development. Juvenile fibroadenoma is a well-circumscribed biphasic neoplasm that often occurs in adolescent girls, characterized by a pericanalicular growth pattern with usual-type epithelial hyperplasia and gynaecomastia-like micropapillary proliferation. Herein, we present an unusual example of a 26-year-old woman with a left breast outer lower quadrant palpable mass. Ultrasonography identified a 5.9 cm lobulated hypoechoic solid mass with scattered small cysts. The preoperative biopsy initially diagnosed a fibroepithelial lesion, considering giant cellular fibroadenoma and phyllodes tumor in the differential. Subsequent complete excision revealed areas of benign phyllodes tumor features closely admixed with distinctive elements such as prominent multiple cysts exhibiting apocrine and papillary apocrine metaplasia, duct papillomatosis, and duct stasis characteristic of juvenile papillomatosis, and hyperplastic ductal epithelium with micropapillary projections demonstrating a pericanalicular growth pattern indicative of juvenile fibroadenoma. The diagnosis was conclusively established as a fibroepithelial lesion with combined features of benign phyllodes tumor, juvenile papillomatosis, and juvenile fibroadenoma. Further investigation uncovered a family history of breast cancer. Molecular analysis revealed a pattern of unique and overlapping mutations within these distinct histopathological areas. This unusual presentation with hybrid features within a single tumor is described for the first time in the literature along with the molecular signature of the individual components.

Clinicopathologic Characteristics of MYC Copy Number Amplification in Breast Cancer.

Introduction. MYC overexpression is a known phenomenon in breast cancer. This study investigates the correlation of MYC gene copy number amplification and MYC protein overexpression with coexisting genetic abnormalities and associated clinicopathologic features in breast cancer patients. Methods. The study analyzed data from 81 patients with localized or metastatic breast cancers using targeted next-generation sequencing and MYC immunohistochemical studies, along with pathological and clinical data. Results. Applying the criteria of MYC/chromosome 8 ratio ≥5, MYC copy number amplified tumors (n = 11, 14%) were associated with invasive ductal carcinoma (91% vs 68%, P = .048), poorly differentiated (grade 3, 64% vs 30%, P = .032), mitotically active (Nottingham mitotic score 3, 71% vs 20%, P = .004), estrogen receptor (ER)-negative (45% vs 12%, P = .008), and triple-negative (56% vs 12%, P = .013) compared to MYC non-amplified tumors. Among MYC-amplified breast cancer patients, those with triple-negative status showed significantly shorter disease-free survival time than non-triple negative MYC-amplified patients (median survival month: 25.5 vs 127.6, P = .049). MYC amplification is significantly associated with TP53 mutation (P = .007). The majority (10 of 11; 91%) of MYC-amplified tumors showed positive c-MYC immunostaining. Conclusion. Breast cancers with MYC copy number amplication display distinct clinicopathologic characteristics indicative of more aggressive behavior.

Identification of Glandular (Acinar)/Tubule Formation in Invasive Carcinoma of the Breast: A Study to Determine Concordance Using the World Health Organization Definition.

CONTEXT.­: The Nottingham Grading System (NGS) developed by Elston and Ellis is used to grade invasive breast cancer (IBC). Glandular (acinar)/tubule formation is a component of NGS. OBJECTIVE.­: To investigate the ability of pathologists to identify individual structures that should be classified as glandular (acinar)/tubule formation. DESIGN.­: A total of 58 hematoxylin-eosin photographic images of IBC with 1 structure circled were classified as tubules (41 cases) or nontubules (17 cases) by Professor Ellis. Images were sent as a PowerPoint (Microsoft) file to breast pathologists, who were provided with the World Health Organization definition of a tubule and asked to determine if a circled structure represented a tubule. RESULTS.­: Among 35 pathologists, the κ statistic for assessing agreement in evaluating the 58 images was 0.324 (95% CI, 0.314-0.335). The median concordance rate between a participating pathologist and Professor Ellis was 94.1% for evaluating 17 nontubule cases and 53.7% for 41 tubule cases. A total of 41% of the tubule cases were classified correctly by less than 50% of pathologists. Structures classified as tubules by Professor Ellis but often not recognized as tubules by pathologists included glands with complex architecture, mucinous carcinoma, and the "inverted tubule" pattern of micropapillary carcinoma. A total of 80% of participants reported that they did not have clarity on what represented a tubule. CONCLUSIONS.­: We identified structures that should be included as tubules but that were not readily identified by pathologists. Greater concordance for identification of tubules might be obtained by providing more detailed images and descriptions of the types of structures included as tubules.

Breast implant-associated anaplastic large-cell lymphoma: A series of two case reports diagnosed by cytopathology.

Breast implant-associated anaplastic large-cell lymphoma (BIA-ALCL) is a rare T-cell lymphoma with a good prognosis. It occurs in association with textured breast implants. Its most common presentation is a late-onset peri-implant effusion. We present two cases of BIA-ALCL diagnosed by cytopathological examination of the fluid collection and describe the cytopathologic findings. Both patients were disease free after implant removal. This report highlights the contribution of the cytopathologic analysis to early diagnosis and definite treatment of BIA-ALCL.

Pathological response in mucinous carcinoma of breast after neoadjuvant therapy - a multi-institutional study.

Although mucinous carcinoma (MC) is considered a favorable histologic subtype of invasive breast cancer (BC), a subset of MC is managed with neoadjuvant therapy (NAT). The clinical and pathologic features of MC following NAT are not well characterized. The aim of this study is to characterize pathologic response in patients with MC treated with NAT, including neoadjuvant endocrine therapy (NET), neoadjuvant chemotherapy (NCT), and Herceptin-targeted NCT (H-NCT). We conducted a retrospective cohort study of 28 patients with MC who received preoperative adjuvant therapy followed by resection from three institutions between 2010 and 2020. Demographic and clinical information were retrieved from the medical records. Pathologic review of the post NAT resection specimens was performed including tumor grading, tumor size, staging, residual tumor cellularity, estrogen receptor (ER) and HER2 status. Nine (32 %) patients with ER+/HER2- MC received NET, 8 (29 %) ER+/HER2- MC were treated with NCT only and 11 (39 %) HER2+ MC received HER2-targeted NCT (H-NCT). The HER2+ MC patients were younger (45 vs. 64 years; p = 0.006). The HER2+ MC were of higher grade (p = 0.03) and more likely to be multifocal (p = 0.008). Only 2 of 28 (7 %) MC (both HER2+) showed complete pathologic response with residual acellular mucin pools. Persistent mass-forming mucin pools were present in 26 (93 %) cases. The residual tumor cellularity was markedly reduced (≤5 %) in H-NCT treated MC (11/11, 100 %), followed by NET group (6/9, 67 %) and NCT only group (4/8, 50 %) (p = 0.011). Similarly, a higher rate of pathologic response (pCR/RCB-I) was observed in H-NCT (7/11, 64 %), followed by NET group (5/9, 56 %), and NCT only group (1/7, 13 %) (p = 0.053). Post-therapy, all HER2+ MC were smaller than 2 cm and ypT size was significantly smaller in H-NCT group (11/11, 100 %) versus combined NET (5/9, 55 %) and NCT only groups (4/8, 50 %) (p = 0.029). We conclude that ER-/HER2+ and ER+/HER2-mucinous carcinomas of the breast show robust pathological response to neoadjuvant HER2 targeted and endocrine therapy, respectively. Our findings suggest that MC may show good response to endocrine therapy.

The correlation of ESR1 genetic aberrations with estrogen receptor and progesterone receptor status in metastatic and primary estrogen receptor-positive breast carcinomas.

Genetic aberrations in the Estrogen Receptor 1 (ESR1) gene have been identified as an important mechanism of resistance to endocrine therapy in metastatic breast carcinoma. In this study, we aimed to correlate ESR1 genetic aberrations with the ER and PR status in paired metastatic and primary breast carcinomas. Patients with ER-positive breast cancer were divided into two groups: ESR1 genetic aberration (n = 26) and wild-type control (n = 29) based on genetic profiling of their metastatic tumors. Clinicopathological features and ER/PR status were analyzed in paired primary and metastatic tumors. Although there was no significant difference in ER expression between the ESR1 aberration and control groups in primary tumors, ER positivity rate in metastatic tumors was significantly higher in the ESR1 aberration group than in the control group (100% vs. 86%, P < .05). ESR1 aberrated cases were associated with more liver metastases than control tumors (46% vs. 10%, P < .01). The ER percentage and intensity slightly increased from primary to metastatic tumors in the ESR1 aberration group compared to a decrease in both in the wild-type group (percentage increase 2% vs. decrease 19%, P = .0594; intensity increase 0.04 vs. decrease 0.8, p < .05). Patients with ESR1 aberrated metastases were more likely than those with wild-type ESR1 metastases to have the following characteristics: 1) ER percentage ≥90% and intensity >2, as well as PR percentage ≥30% and intensity >1 in metastatic tumors; 2) ER percentage ≥90% and PR percentage ≥70% in primary tumors; and 3) slightly increase in ER percentage and intensity from primary to metastatic tumors. Based on the ER/PR parameters of paired primary and metastatic breast cancer, ESR1 aberration in metastasis may be predicted.

Prognostic impact of reduced HER2 protein expression in post-neoadjuvant therapy resection specimens: A single institution experience and review of the literature.

BACKGROUND: Retesting for Human epidermal growth factor receptor-2 (HER2) in post-neoadjuvant therapy resection is variable, and data is conflicting regarding the prognostic significance of changes in HER2 expression pre and post therapy. METHODS: We identified 104 patients with localized HER2 IHC 3+ breast cancer who received neoadjuvant trastuzumab(T)/pertuzumab(P) containing chemotherapy at Yale Cancer Center between 2012 and 2022. Patients were divided into 3 cohorts by response and HER2 IHC in the residual disease: Cohort 1 pathologic complete response (pCR), Cohort 2 pre-treatment IHC 3+/post treatment IHC 1+/2+, and Cohort 3 pre-treatment IHC 3+/post-treatment IHC 3+. Kaplan-Meier survival analysis was performed to assess recurrence free survival at 36 months. RESULTS: The overall pCR rate was 62.5% (65/104), while 37.5% (39/104) of patients had residual disease (RD). Among patients with RD, 58.9% (23/39) remained IHC 3+ and 41.1% (16/39) had reduced HER2 expression IHC1+ or 2+. In patients with HER2 IHC 3+ RD, 26% (6/23) developed local recurrence or distant metastasis while none of patients with post NAT HER2 IHC 1+ or 2+ RD had relapse (p = 0.0309). In patients with pCR, 6.15% (4/65) had recurrence. Kaplan-Meier survival analysis revealed superior disease-free survival in patients with reduced HER2 IHC expression compared to those with remained IHC 3+ (log rank p = 0.004). CONCLUSION: We conclude that reduced HER2 expression by IHC following neoadjuvant treatment was associated with lower recurrence rates in HER2 IHC 3+ breast cancer. If confirmed, RD HER2 IHC expression could be used as a prognostic biomarker to stratify patients in adjuvant trials and identify patients who may benefit from more intensive adjuvant therapy and post therapy surveillance.

AMACR Expression is a Potential Diagnostic Marker in Apocrine Lesions of Breast, and is Associated with High Histologic Grade and Lymph Node Metastases in Some Invasive Apocrine Breast Cancers.

BACKGROUND: Carcinoma with apocrine differentiation (AC) is a subtype of breast carcinoma with apocrine features in >90% of the tumor. Molecular studies demonstrate AC has high expression of androgen receptor (AR) mRNA. Pure AC lack estrogen receptor (ER), progesterone receptor (PR), and express AR, with variable human epidermal growth factor 2 (HER2) status. Currently, in triple negative AC, no targetable therapies or specific diagnostic markers exist. MATERIALS AND METHODS: α-Methylacyl CoA racemase (AMACR) expression was investigated as a marker of apocrine differentiation using a single-plex immunoperoxidase stain, and a novel AMACR/p63 dual stain in a subset of cases, across 1) benign apocrine lesions (apocrine metaplasia, adenosis) 2) apocrine DCIS (ADCIS), 3) AC/ invasive ductal carcinoma (IDC) with apocrine features, 4) non-apocrine triple negative breast cancer (TNBC) and 5) IDC, no special type. A sub-set of cases were evaluated by tissue microarray. RESULTS: AMACR expression was increased in both AC and ADCIS, with minimal expression in benign breast tissue, TNBC and IDC, NST cases. In invasive cases, those with positive AMACR (>5% positivity) were significantly associated with higher histologic grade (P = .006), initial N stage (chi squared 0.044), and lack of ER or PR expression (both P < .001), with no correlation with overall survival. Analysis of TCGA breast cancer datasets revealed AMACR expression was significantly higher in molecularly defined apocrine carcinomas relative to basal and luminal subtypes. Moreover, high AMACR expression predicted worse relapse-free and distant-metastasis free survival, among both ER-/PR-/Her2- and ER-/PR-/Her2+ breast cancer cohorts (log-rank P = .081 and .00011, respectively). CONCLUSION: AMACR represents a promising diagnostic and prognostic marker in apocrine breast lesions. Further study is needed to determine the biologic and clinical significance of this protein in AC.