Frequent upregulation of HER2 protein in hormone-receptor-positive HER2-negative breast cancer after short-term neoadjuvant endocrine therapy.

BACKGROUND: Endocrine resistant metastatic disease develops in ~ 20-25% of hormone-receptor-positive (HR+) breast cancer (BC) patients despite endocrine therapy (ET) use. Upregulation of HER family receptor tyrosine kinases (RTKs) represent escape mechanisms in response to ET in some HR+ tumors. Short-term neoadjuvant ET (NET) offers the opportunity to identify early endocrine escape mechanisms initiated in individual tumors. METHODS: This was a single arm, interventional phase II clinical trial evaluating 4 weeks (± 1 week) of NET in patients with early-stage HR+/HER2-negative (HER2-) BC. The primary objective was to assess NET-induced changes in HER1-4 proteins by immunohistochemistry (IHC) score. Protein upregulation was defined as an increase of ≥ 1 in IHC score following NET. RESULTS: Thirty-seven patients with cT1-T3, cN0, HR+/HER2- BC were enrolled. In 35 patients with evaluable tumor HER protein after NET, HER2 was upregulated in 48.6% (17/35; p = 0.025), with HER2-positive status (IHC 3+ or FISH-amplified) detected in three patients at surgery, who were recommended adjuvant trastuzumab-based therapy. Downregulation of HER3 and/or HER4 protein was detected in 54.2% of tumors, whereas HER1 protein remained low and unchanged in all cases. While no significant volumetric reduction was detected radiographically after short-term NET, significant reduction in tumor proliferation rates were observed. No significant associations were identified between any clinicopathologic covariates and changes in HER1-4 protein expression on multivariable analysis. CONCLUSION: Short-term NET frequently and preferentially upregulates HER2 over other HER family RTKs in early-stage HR+/HER2- BC and may be a promising strategy to identify tumors that utilize HER2 as an early endocrine escape pathway. CLINICAL TRIAL REGISTRY: Trial registration number: NCT03219476.

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.

Giant juvenile fibroadenomas with and without prominent pseudoangiomatous stromal hyperplasia (PASH)-like change: clinicopathological and molecular characteristics.

AIMS: Juvenile fibroadenomas (JFA) are biphasic fibroepithelial lesions (FEL) usually occurring in adolescent female patients. Giant (G) JFA, like other FEL, may exhibit prominent pseudoangiomatous stromal hyperplasia (PASH)-like change. We sought to determine clinicopathological and molecular characteristics of GJFA with and without PASH. METHODS AND RESULTS: Archives were searched for cases of GJFA (1985-2020). All were stained for androgen receptor (AR), beta-catenin, CD34 and progesterone receptor (PR). Cases were sequenced using a custom 16-gene panel - MED12 (exons 1 and 2), TERT promoter (-124C>T and -146Ctable>T), SETD2, KMT2D, RARA (exons 5-9), FLNA, NF1, PIK3CA (exons 10, 11 and 21), EGFR, RB1, BCOR, TP53, PTEN, ERBB4, IGF1R and MAP3K1. Twenty-seven GJFA from 21 female patients aged 10.1-25.2 years were identified. Size ranged from 5.2 to 21 cm. Two patients had multiple, bilateral and later recurrent GJFA. Thirteen (48%) cases showed prominent PASH-like stroma. All were positive for stromal CD34, negative for AR and beta-catenin and one case showed focal PR expression. Sequencing showed MAP3K1 and SETD2 mutations in 17 samples, with KMT2D, TP53 and BCOR aberrations in 10 (45%), 10 (45%) and seven (32%) cases, respectively. Tumours with a PASH-like pattern had higher prevalence of SETD2 (P = 0.004) and TP53 (P = 0.029) mutations, while those without PASH had more RB1 mutations (P = 0.043). MED12 mutation was identified in one case. TERT promoter mutation was observed in four (18%), including two recurrences. CONCLUSIONS: Gene mutations along more advanced phases of the proposed FEL pathogenetic pathway in GJFA are unusual, and suggest a mechanism for more aggressive growth in these tumours.

Contemporary evaluation of estrogen receptor and progesterone receptor expression in breast cancer-associated stroma.

PURPOSE: To investigate nuclear estrogen receptor α (ERα) and progesterone receptor (PR) immunohistochemistry (IHC) patterns in the stroma surrounding invasive carcinoma and assess associations with clinicopathologic features. METHODS: A retrospective database search (1/2017-12/2020) identified breast core biopsies with invasive carcinoma. ERα/PR IHC expression in invasive carcinoma and stromal cells was categorized visually as positive (> 10%), low positive (1-10%) or negative (< 1%). Tumors were divided into 4 subtypes by IHC: Luminal, Luminal HER2, HER2 enriched, and triple negative. Clinicopathologic features associated (univariate p-value < 0.15) with ERα/PR stromal expression were investigated further using stepwise multivariable logistic regression. RESULTS: Of 1512 biopsies, 1278 had accessible IHC. 55.6% (711/1278) and 10.4% (133/1274) of cases showed cancer-associated stromal fibroblast expression of ERα and PR, respectively. Stromal ER positivity was significantly associated with use of the Ventana (with SP1 clone) versus Leica (with 6F11 clone) platform and in cases with Luminal cancer subtype. PR stromal expression was significantly associated with Luminal subtype, obesity, and younger age. CONCLUSIONS: Expression of ERα and PR in breast cancer-associated stroma showed associations that suggest both biologic and analytic influence. Reproducible expression patterns may inform expansion of ERα/PR guidelines for the assessment of internal controls.

Primary Breast Neuroendocrine Tumors: An Analysis of the National Cancer Database.

BACKGROUND: Primary breast neuroendocrine tumors (BNETs) represent < 1% of breast cancers. Diagnosing BNETs can be challenging, and a limited amount of cohort data currently exists in literature. We aimed to describe primary BNET characteristics, treatment modalities, and survival outcomes through the National Cancer Database (NCDB). METHODS: A retrospective cohort analysis was performed using the NCDB from 2004 to 2017. BNET cases were compared with patients with invasive ductal carcinoma (IDC). A matched IDC cohort was created by matching patient age, race, and disease stage. Kaplan-Meier analysis was performed, and hazard ratios (HR) were calculated through the bootstrap sampling method. RESULTS: A total of 1389 BNET and 1,967,401 IDC cases were identified. When compared with IDC patients, BNET patients were older, had more comorbidities, and were more often male (p < 0.01). BNETs were larger, higher grade, and more frequently hormone receptor negative (p < 0.01). While BNET patients were treated with surgery and radiotherapy (p < 0.01) less often compared with IDC patients, they presented at later disease stage (p < 0.001) and received systemic treatment more frequently (53.5% vs. 40%, p < 0.01). Patients with BNET had increased mortality compared with the matched IDC cohort: stage 1 HR 1.8, stage 2 HR 2.0, stage 3 HR 1.8, and stage 4 HR 1.5 (p < 0.001 for all). CONCLUSION: Patients with BNET tend to present at higher clinical stages, are more frequently hormone receptor negative, and have inferior overall survival compared with patients with IDC. Further treatment strategies and studies are needed to elucidate optimal therapies to maximize patient outcomes.

Unveiling the histopathologic spectrum of MRI-guided breast biopsies: an institutional pathological-radiological correlation.

PURPOSE: Breast magnetic resonance imaging (MRI) has high sensitivity but suffers from low specificity, resulting in many benign breast biopsies for MRI-detected lesions. We sought to compare histologic findings between patients who underwent MRI-guided breast biopsy versus biopsy via other imaging modalities as well as to examine features associated with malignancy in the MRI cohort to help inform MRI-biopsy practice. METHODS: A 2-year (2018-2019) retrospective review of breast biopsies at our enterprise was conducted. Biopsies were categorized as stereotactic, ultrasound, MRI, or palpation guided. Pathology was categorized as benign (further divided into nine categories), atypical, or malignant (subdivided into in situ and invasive carcinoma). Pathology was compared between biopsy groups. Clinical, pathologic, and imaging features were compared between pathology groups within the MRI cohort. RESULTS: 5828 biopsies from 4154 patients were reviewed, including 548 MRI-guided biopsies with stratification of MRI-biopsy pathology as follows: 69% benign, 13.8% atypical, and 17.2% malignant. Among benign MRI biopsies, there was higher frequency of "clustered cysts with papillary apocrine metaplasia" (56/548; 10.2%) and lower rate of fibroadenoma/fibroadenomatous change (55/548; 10%) compared to other modalities (158 or 3% and 1144 or 21.7% of 5280 biopsies, respectively). Multivariate analysis revealed indication of breast cancer (p < .0001), ipsilateral cancer (p < .0001) and rapid initial phase kinetics (p = .017) to remain significantly associated with malignant MRI-biopsy pathology. CONCLUSIONS: A concurrent or recent breast cancer diagnosis was most predictive of malignancy on MRI-guided breast biopsy. Combined MRI feature evaluation and radiologic-pathologic concordance activities may allow for prognostic refinement and improved risk stratification.

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.

Assessing the value of second opinion pathology review.

BACKGROUND: Second opinion review of pathology cases can identify diagnostic errors that impact patient care. OBJECTIVE: We sought out to determine discrepancy rates and clinical impact of review of pathology cases to reassess our policy of review on all second opinion cases. METHODS: All second opinion pathology cases over 1 year (2018) were retrospectively reviewed for discrepancy, multiple pathologist review and clinicopathologic features via chart and slide review. Cases were categorized as no significant discordance, major discordance without management change and major discordance with management change. RESULTS: Among 4239 second opinion cases, 3.7% (156/4239) had major discordance with no change in management and 1% (42/4239) had major discordance with change in management. Discordance was significantly associated with multiple pathologist review at our institution (P < 0.001). Highest rates of discordance were observed for thyroid fine needle aspiration (15.3%, 26/170), tissue biopsy of bone/soft tissue (9.6%), endocrine (8.8%), genitourinary (6.7%), gynecologic (6.2%), hematopathology (4%), gastrointestinal/liver (3.7%) and thoracic (3%) sites. CONCLUSIONS: Our study showed a 1% major discordance rate with resulting significant change in clinical management, spread across nearly all subspecialties. Thus, we support recommendations for review of relevant outside pathology material for all patients for which review has the potential to illicit management change such as instituting a major medical or surgical therapy.

A high mitotic score in breast cancer after neoadjuvant chemotherapy is predictive of outcome and associated with a distinct morphology.

AIMS: Neoadjuvant chemotherapy (NAC) is frequently used for the treatment of breast cancer. We sought to analyse the clinical, morphological and immunohistochemical features of tumours from patients who did not achieve pathological complete response following NAC. METHODS AND RESULTS: We identified stage I-III post-NAC breast cancers from surgical resections (2000-2016) with evaluable residual invasive carcinoma [ypT1a(m) or greater and ≥15% tumour cellularity]. One hundred and forty-three tumours from 142 patients were included. On univariable analysis, a high (score 3) post-NAC mitotic score (as compared with 1 or 2) was significantly associated with invasive ductal carcinoma (IDC) subtype (P = 0.023), high grade, pushing borders with zones of necrosis, hormone receptor and triple-negative status, lack of hormonal therapy, higher cellularity (P < 0.001), and a higher percentage of tumour-infiltrating lymphocytes (P = 0.016). Multivariable analysis showed a high post-NAC mitotic score to be significantly associated with recurrence, distant metastasis, and shortened survival (hazard ratios of 5.73, 4.49, and 3.68, respectively). High post-NAC mitotic score tumours (n = 32) were IDC and had a high Ki67 proliferation index (median, 55%). Of these, 24 (75%) had pushing borders with zones of necrosis; 19 (79.2%) of these had necrosis on preoperative imaging, and 24 (75%), 15 (46.9%) and four (12.5%) lacked androgen receptor, GATA-3 and cytokeratin 18 expression, respectively. CONCLUSIONS: High post-NAC mitotic score breast cancers cause high morbidity and mortality, frequently have pushing borders and zones of necrosis, and may show loss of common 'breast cancer markers'. Our findings support that necrosis in pretreatment studies and post-NAC mitotic score should be routinely reported, as they offer significant additional prognostic information to guide management.

Pleomorphic Lobular Carcinoma In Situ: Imaging Features, Upgrade Rate, and Clinical Outcomes.

OBJECTIVE: Pleomorphic lobular carcinoma in situ (PLCIS) is an aggressive subtype of lobular carcinoma in situ treated similarly to ductal carcinoma in situ. The purpose of this study was to determine the imaging findings, upgrade rate of PLCIS at core needle biopsy (CNB), and the treatment and outcomes of these patients. MATERIALS AND METHODS: This retrospective single-institution study included women with PLCIS at CNB or excisional biopsy without concomitant DCIS or invasive carcinoma between January 1, 1999, and July 20, 2016. Imaging findings, detection mode, treatment, and outcomes were reviewed. Retrospective review of the images was performed. Upgrade rate to ductal carcinoma in situ or invasive carcinoma at lumpectomy was calculated. RESULTS: Twenty-one patients had a finding of PLCIS at CNB (n = 16) or excisional biopsy (n = 5). Four of 15 (27%; 95% CI, 4-49%) cases of PLCIS at CNB were upgraded to DCIS (two cases) or invasive lobular cancer (two cases) at lumpectomy (one patient declined excision). No unique mammographic features were predictive of need to upgrade or extent of disease. Among the patients with pure PLCIS (not upgraded), 13 of 16 (81%) presented with fine pleomorphic calcifications on screening mammograms, 1 of 16 (6%) with distortion and calcifications, 1 of 16 (6%) with a mass, and 1 of 16 (6%) with nonmass enhancement at MRI. The median imaging size was 11 mm (mean, 14 mm; range, 3-47 mm). Twelve of 16 (75%) patients were treated with lumpectomy and 4 of 16 (25%) with mastectomy. Eight of 16 (50%) patients received adjuvant hormonal therapy, and 2 of 16 (17%) received radiation. There were no local recurrences. CONCLUSION: PLCIS most commonly presented as fine pleomorphic calcifications on mammograms and had a high upgrade rate after CNB. CNB diagnosis of PLCIS requires surgical excision.

A rapid triage protocol to optimize cold ischemic time for breast resection specimens.

Prolonged time from specimen excision to adequate formalin exposure, or cold ischemic time (CIT), negatively impacts estrogen receptor (ER), progesterone receptor (PR) and HER-2 biomarker studies routinely performed on breast specimens. Current guidelines recommend CIT of ≤1 h. Since formalin penetrates resections slowly, optimal fixation requires incision. We evaluated the efficacy of a rapid triage protocol developed to optimize CIT. We identified 2821 specimens: 650 (23.0%) excisional biopsies (EB), 1051 (37.3%) lumpectomies, and 1120 (39.7%) mastectomies. CIT was available for 2362 (83.7%), with 1845 (78.1%) ≤1 h and 2323 (98.3%) ≤4 h. IHC was performed in 533/2821 (18.9%) and was associated with lumpectomy and mastectomy procedures when compared to EB. However, IHC was also performed on 11.1% (72/650) of EB specimens despite EB being significantly less likely to have CIT recorded (468/650; 72% for EB vs. 1894/2171; 87.2% for lumpectomies/mastectomies). Our study highlights the need for rapid triage of breast resections with known or suspected malignant diagnoses and outlines our procedure for optimizing CIT. Additionally, we advocate treating ALL breast resections as having the potential of being malignant and requiring biomarker studies for which optimal CIT is of great importance.

Discordance between original and central laboratories in ER and HER2 results in a diverse, population-based sample.

PURPOSE: To investigate the discordance between original and central laboratories in estrogen receptor (ER) status, in tumors originally deemed to be ER-negative, and in HER2 status in a diverse population-based sample. METHODS: In a follow-up study of 1785 women with Stage I-III breast cancer diagnosed between 2005 and 2007 in the Detroit and Los Angeles County SEER registry catchment areas, participants were asked to consent to reassessment of ER (in tumors originally deemed to be ER-negative) and HER2 status on archival tumor samples approximately four years after diagnosis. Blocks were centrally prepared and analyzed for ER and HER2 using standardized methods and the guidelines of the American Society of Clinical Oncology and the College of American Pathologists. Analyses determined the discordance between original and central laboratories. RESULTS: 132 (31%) of those eligible for ER reassessment and 367 (21%) eligible for HER2 reassessment had archival blocks reassessed centrally. ER discordance was only 6%. HER2 discordance by immunohistochemistry (IHC) was 26%, but final HER2 results-employing FISH in tumors that were IHC 2+ at the central laboratory-were discordant in only 6%. Half of the original laboratories did not perform their own assays. CONCLUSIONS: Discordance between original and central laboratories in two large metropolitan areas was low in this population-based sample compared to previously reported patient samples. Centralization of testing for key pathology variables appears to be occurring in many hospitals. In addition, quality improvement efforts may have preceded the publication and dissemination of specialty society guidelines.

Clinicopathological findings in female-to-male gender-affirming breast surgery.

AIMS: Gender dysphoria is a diagnosis whereby an individual identifies as the opposite gender. The management of patients seeking female-to-male (FTM) transition includes hormonal therapy and surgical intervention, including mastectomy. The aim of this study was to characterize the immunohistological findings in resection specimens from FTM patients. METHODS AND RESULTS: We reviewed 68 cases (67 patients, one with re-excision) of FTM breast tissue resection by collecting clinical data, reviewing breast imaging and pathology reports (gross fibrous density, specimen weight, and number of cassettes submitted), and reviewing pathology slides [number of tissue pieces submitted, number of terminal duct lobule units (TDLUs), and the presence of histological findings]. Significant histological findings were present in 51 of 68 (75.0%) cases, including one case (1.5%) of flat epithelial atypia. Fibrocystic changes were the most common finding (27/68, 39.7%), followed by gynaecomastoid change, fibrotic stage, (22/68, 32.4%), and fibroadenomatoid change (11/68, 16.2%). Fibrocystic change was associated with increased numbers of TDLUs, and gynaecomastoid change was associated with lower body mass index and decreased numbers of TDLUs. Gynaecomastoid change showed a moderate proportion of luminal epithelial cells with strong-intensity immunohistochemical staining for oestrogen receptor, progesterone receptor, and androgen receptor, and a three-layered epithelium demonstrated by the use of cytokeratin 5/6 immunohistochemistry. CONCLUSIONS: We identified gynaecomastoid change at a significantly higher rate than previously reported in female patients. We support the continued gross and histological evaluation of FTM specimens in light of the identification of atypia in one case.

Heterologous Liposarcomatous Differentiation in Malignant Phyllodes Tumor is Histologically Similar but Immunohistochemically and Molecularly Distinct from Well-differentiated Liposarcoma of Soft Tissue.

Malignant phyllodes tumor (PT) infrequently displays heterologous differentiation, and when present is most often liposarcomatous. We identified five cases of malignant PT with regions identical to well-differentiated liposarcoma (WDLS) of soft tissue and evaluated them for MDM2 and CDK4 gene expression and amplification using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), respectively. Despite indistinguishable morphology all cases of malignant PT with WDLS-like liposarcomatous differentiation were negative for MDM2 and CDK4 IHC and FISH, supporting different underlying pathogenesis.

Ductal carcinoma in situ with distorting sclerosis on core biopsy may be predictive of upstaging on excision.

AIMS: The aim of this study was to examine clinicopathological features of patients with core biopsy diagnoses of ductal carcinoma in situ (DCIS) that may predict invasion on subsequent excision, as upstaging has significant implications regarding the need for axillary staging via sentinel lymph node biopsy (SLNB). METHODS AND RESULTS: We identified 186 patients with a diagnosis of DCIS as the highest-stage lesion on core biopsy. Pathological and clinical features were assessed via slide and chart review, respectively. Distorting sclerosis was defined as irregular angulation of glands involved by DCIS but lacking definite invasion according to histology and/or immunohistochemical staining for myoepithelial markers. Thirty-two of 186 (17.2%) cases had upstaging to either microinvasive (nine) or invasive (23) ductal carcinoma. SLNB was performed in 29 of 32 (90.6%) cases with upstaging and in 55 of 154 (35.7%) cases without (P < 0.0001). Upstaging was significantly associated with the presurgical variables of radiological mass (P = 0.009) and distorting sclerosis (P = 0.0005) and the postsurgical feature of multifocality (P < 0.0001). CONCLUSIONS: Sentinel lymph node biopsy is frequently performed for patients with upstaging from DCIS on core biopsy to microinvasive or invasive carcinoma on excision. DCIS with distorting sclerosis without definite invasion on core biopsy may be predictive of upstaging. This feature may be useful in selecting patients to undergo SLNB at the time of excision to avoid reoperation.