Best practices for achieving consensus in HER2-low expression in breast cancer: current perspectives from practising pathologists.

AIMS: Human epidermal growth factor receptor 2 (HER2) expression is an important biomarker in breast cancer (BC). Most BC cases categorised as HER2-negative (HER2-) express low levels of HER2 [immunohistochemistry (IHC) 1+ or IHC 2+/in-situ hybridisation not amplified (ISH-)] and represent a clinically relevant therapeutic category that is amenable to targeted therapy using a recently approved HER2-directed antibody-drug conjugate. A group of practising pathologists, with expertise in breast pathology and BC biomarker testing, outline best practices and guidance for achieving consensus in HER2 IHC scoring for BC. METHODS AND RESULTS: The authors describe current knowledge and challenges of IHC testing and scoring of HER2-low expressing BC and provide best practices and guidance for accurate identification of BCs expressing low levels of HER2. These expert pathologists propose an algorithm for assessing HER2 expression with validated IHC assays and incorporate the 2023 American Society of Clinical Oncology and College of American Pathologist guideline update. The authors also provide guidance on when to seek consensus for HER2 IHC scoring, how to incorporate HER2-low into IHC reporting and present examples of HER2 IHC staining, including challenging cases. CONCLUSIONS: Awareness of BC cases that are negative for HER protein overexpression/gene amplification and the related clinical relevance for targeted therapy highlight the importance of accurate HER2 IHC scoring for optimal treatment selection.

Correlation of the Ki67 Working Group prognostic risk categories with the Oncotype DX Recurrence Score in early breast cancer.

BACKGROUND: The relationship between Ki67 assessed by immunohistochemistry (IHC) and the Oncotype DX Recurrence Score (RS) is unclear. The objective of this study was to determine the correlation between the 21-gene RS and IHC-measured Ki67 with the prognostic classification groups recommended by the International Ki67 Working Group (IKWG). METHODS: The authors performed a retrospective chart review of women who had hormone receptor (HR)-positive, human epidermal growth factor receptor 2-negative early breast cancer with zero to three positive lymph nodes and both Ki67 and the 21-gene RS performed at their institution from 2013 to 2021. Patients were categorized into low (≤5%), intermediate (6%-29%), and high Ki67 groups (≥30%) according to IKWG recommendations. Overall agreement and risk-stratified agreement between Ki67 and RS were assessed with the proportion of agreement and the κ statistic. RESULTS: The study included 525 patients with HR-positive breast cancer. Among the 49% of patients with intermediate Ki67 values of 6%-29%, the distribution of low (0-10), intermediate (11-25), and high RS (26-100) was 19%, 66%, and 15%, respectively. There was slight agreement (κ = 0.01-0.20) between Ki67 and RS (κ = 0.027) in the overall population, although this was not significant (p = .1985). There was fair agreement (κ = 0.21-0.40) between high Ki67 and RS values (κ = 0.280; p < .0001). A higher progesterone receptor percentage was associated with lower RS values (p > .0001) but not lower Ki67 values. A positive nodal status and a larger tumor size were associated with higher Ki67 values (p = .0059 and p < .0001) but not with RS. CONCLUSIONS: In this group of patients selected to have a 21-gene RS, there was no significant correlation between Ki67 and RS in the overall population, and there was fair agreement between high Ki67 and high RS values. LAY SUMMARY: In patients with early-stage, hormone receptor-positive breast cancer, decisions on adjuvant chemotherapy are based on certain biological features of the cancer and genomic assays such as the Oncotype DX Recurrence Score (RS). The goal of this study was to determine the correlation between Ki67, a marker of proliferation, and the Oncotype DX RS, a 21-gene assay demonstrated to be predictive of an adjuvant chemotherapy benefit in patients with early-stage breast cancer. In 525 patients, the authors did not find a significant correlation between Ki67 and RS.

Mastectomy or Margin Re-excision? A Nomogram for Close/Positive Margins After Lumpectomy for DCIS.

BACKGROUND: Anatomic extent of ductal carcinoma in situ (DCIS) may be uncertain in spite of clinical, pathologic, and imaging data. Consequently close/positive margins are common with lumpectomy for DCIS and often lead to a challenge in deciding whether to perform a re-excision or mastectomy. PATIENTS AND METHODS: From a single health system, we identified cases of lumpectomy for DCIS with close/positive margins who underwent re-excision for the purpose of constructing a nomogram. In total, 289 patients were available for analysis. The patients were randomly divided into two sets allocating 70% to the modeling and 30% to the validation set. A multivariable logistic regression model was used to estimate the probability of overall positive margin status using multiple clinicopathologic predictors. Nomogram validation included internal tenfold cross-validation, internal bootstrap validation, and external validation for which a concordance index was calculated to assess the external validity. RESULTS: Significant predictors of persistent positive margins from regression modeling included necrosis at diagnosis (non-comedo or comedo); DCIS not associated with calcifications on core biopsy; high-grade DCIS; progesterone receptor positivity; and number of positive margins at initial surgery. When subjected to internal validation, the nomogram achieved an uncorrected concordance index of 0.7332, a tenfold cross-validation concordance index of 0.6795, and a bootstrap-corrected concordance index of 0.6881. External validation yielded an estimated concordance index of 0.7095. CONCLUSION: Using clinical and pathologic variables from initial diagnosis and surgery for DCIS, this nomogram predicts persistent positive margins with margin re-excision, and may be a valuable tool in surgical decision-making.

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.

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.

Secondary Invasive Breast Events among Patients with Hormone-Positive Breast Cancer and High-Risk Oncotype DX Recurrence Scores 26-30 and ≥31.

BACKGROUND: The Oncotype DX Recurrence Score (ODx RS) is the most widely adopted genomic assay used to guide treatment for patients with early-stage, hormone-positive (HR+) breast cancer (BC), with higher scores predicting greater risk of recurrence and benefit from chemotherapy. Patients with ODx RS >25 typically recieve adjuvant chemotherapy; however, data regarding efficacy of chemotherapy for reducing recurrence in this population have been mixed. OBJECTIVES: This study aimed to evaluate outcomes of patients with early-stage HR+ BC with high-risk ODx RS (26-30 and ≥31) in order to assess treatment patterns and outcomes. We hypothesized that the benefit of chemotherapy in these groups may be minimal and that select patients may forgo chemotherapy in favor of more aggressive endocrine therapy and ovarian suppression. METHODS: We performed a retrospective analysis of 515 patients with early-stage, HR+ BC with high-risk ODx RS 26-30 and ≥31 treated between 2006 and 2018. Patients were stratified by RS: low-risk (≤10), intermediate-risk (11-25), and high-risk (≥26). The Kaplan-Meier method was used to estimate the time to secondary invasive breast events (SIBE) or distributions overall and among different RS groups with the log rank test used to compare distributions between groups. RESULTS: Rates of chemotherapy administration were 7% among the low-risk group, 18% among the intermediate-risk group, and 83% among high-risk patients with 41 SIBE (8%) reported. When stratified by ODx RS, 5-year rates of SIBE were 4%, 6%, and 16% for low-risk, intermediate-risk, and high-risk RS, respectively. Among the 27 lymph node (LN)-negative patients with ODx RS 26-30, 74% received chemotherapy. The 5-year rate of SIBE was 25% among patients who received chemotherapy and 33% among those who did not (p = 0.5489). Among the 23 LN-negative patients with ODx RS ≥31, 91% of patients received chemotherapy. The 5-year rate of SIBE was 0% both with and without chemotherapy. CONCLUSIONS: There was no statistically significant difference in SIBE for patients with high-risk ODx RS based on chemotherapy treatment. More aggressive endocrine therapy with ovarian suppression has become an alternative to chemotherapy among patients with intermediate-risk ODx RS (16-25). This approach may be useful among patients with high-risk ODx RS, with additional studies needed in this patient population.

Response in breast vs axilla after neoadjuvant treatment and implications for nonoperative management of invasive breast cancer.

Improved imaging and neoadjuvant chemotherapy (NAT) have led to higher pathologic complete response rates (pCR) in patients with invasive breast cancer. This has questioned the necessity of surgery and axillary lymph node (ALN) dissection in these patients. Prospective clinical trials are implementing extensive core biopsies of the tumor bed of patients with clinical complete response as a means to identify and spare them breast surgery. In addition, it is anticipated that patients with pCR are most likely going to have no or minimal disease in ALN as well. To verify the feasibility of these trials, we performed a pathologic analysis of all our patients who have undergone NAT from 2009 to present. Using pathology data base, we identified 362 patients treated with neoadjuvant chemotherapy followed by surgery. Clinical and pathologic information including gross and microscopic descriptions as well as biomarker status was collected. pCR was 50% for patients with negative ALN pretreatment but only 28% for patients with positive ALN at diagnosis. Despite achieving pCR in the breast, up to 10% of patients with positive ALN and 1% with negative ALN had persistent disease. Eight percent of patients that were presumed to have no ALN disease either clinically and or by imaging were found to have metastatic carcinoma in ALN. The metastases were predominantly (80%) <5 mm, and not palpable on physical examination and or due to biopsy sampling error. pCR in breast and ALN directly correlated with tumor size, ALN disease, and Her2 positive and triple negative receptor phenotype. In breast cancer patients who are node positive at time of diagnosis with pCR in the breast after neoadjuvant chemotherapy, residual lymph node disease was very uncommon. Further study is warranted to select patients who may avoid breast and axillary surgery post neoadjuvant chemotherapy.

Interobserver variability in upfront dichotomous histopathological assessment of ductal carcinoma in situ of the breast: the DCISion study.

Histopathological assessment of ductal carcinoma in situ, a nonobligate precursor of invasive breast cancer, is characterized by considerable interobserver variability. Previously, post hoc dichotomization of multicategorical variables was used to determine the "ideal" cutoffs for dichotomous assessment. The present international multicenter study evaluated interobserver variability among 39 pathologists who performed upfront dichotomous evaluation of 149 consecutive ductal carcinomas in situ. All pathologists independently assessed nuclear atypia, necrosis, solid ductal carcinoma in situ architecture, calcifications, stromal architecture, and lobular cancerization in one digital slide per lesion. Stromal inflammation was assessed semiquantitatively. Tumor-infiltrating lymphocytes were quantified as percentages and dichotomously assessed with a cutoff at 50%. Krippendorff's alpha (KA), Cohen's kappa and intraclass correlation coefficient were calculated for the appropriate variables. Lobular cancerization (KA = 0.396), nuclear atypia (KA = 0.422), and stromal architecture (KA = 0.450) showed the highest interobserver variability. Stromal inflammation (KA = 0.564), dichotomously assessed tumor-infiltrating lymphocytes (KA = 0.520), and comedonecrosis (KA = 0.539) showed slightly lower interobserver disagreement. Solid ductal carcinoma in situ architecture (KA = 0.602) and calcifications (KA = 0.676) presented with the lowest interobserver variability. Semiquantitative assessment of stromal inflammation resulted in a slightly higher interobserver concordance than upfront dichotomous tumor-infiltrating lymphocytes assessment (KA = 0.564 versus KA = 0.520). High stromal inflammation corresponded best with dichotomously assessed tumor-infiltrating lymphocytes when the cutoff was set at 10% (kappa = 0.881). Nevertheless, a post hoc tumor-infiltrating lymphocytes cutoff set at 20% resulted in the highest interobserver agreement (KA = 0.669). Despite upfront dichotomous evaluation, the interobserver variability remains considerable and is at most acceptable, although it varies among the different histopathological features. Future studies should investigate its impact on ductal carcinoma in situ prognostication. Forthcoming machine learning algorithms may be useful to tackle this substantial diagnostic challenge.

Evaluation of surgically excised breast tissue microstructure using wide-field optical coherence tomography.

BACKGROUND: Currently, positive margins at lumpectomy contribute to health care cost, patient anxiety, and treatment delay. Multiple technology solutions are being explored with the aim of lowering re-excision rates for breast-conserving surgery (BCS). We examined wide-field optical coherence tomography (WF-OCT), an innovative adjunct intraoperative imaging tool for tissue visualization of margins. METHODS: This IRB-approved pilot study included women with invasive or in situ carcinoma scheduled for primary BCS. Lumpectomy specimens and any final/revised margins were imaged by optical coherence tomography immediately prior to standard histological processing. The optical coherence tomography used provided two-dimensional, cross-sectional, real-time depth visualization of the margin widths around excised specimens. A volume of images was captured for 10 × 10 cm tissue surface at high resolution (sub-30 µm) to a depth of 2 mm. Integrated interpretation was performed incorporating final pathology linked with the optical image data for correlation. RESULTS: Wide-field optical coherence tomography was performed on 185 tissue samples (50 lumpectomy specimens and 135 additional margin shaves) in 50 subjects. Initial diagnosis was invasive ductal carcinoma (IDC) in 10, ductal carcinoma in situ (DCIS) in 14, IDC/DCIS in 22, invasive lobular carcinoma (ILC) in 2, ILC/DCIS in 1, and sarcoma in 1. Optical coherence tomography was concordant with final pathology in 178/185 tissue samples for overall accuracy of 86% and 96.2% (main specimen alone and main specimen + shave margins). Of seven samples that were discordant, 57% (4/7) were considered close (DCIS < 2 mm from margin) per final pathology. CONCLUSION: Wide-field optical coherence tomography demonstrated concordance with histology at tissue margins, supporting its potential for use as a real-time adjunct intraoperative imaging tool for margin assessment. Further studies are needed for comprehensive evaluation in the intraoperative setting.

Observation versus excision of lobular neoplasia on core needle biopsy of the breast.

PURPOSE: Controversy surrounds management of lobular neoplasia (LN), [atypical lobular hyperplasia (ALH) or lobular carcinoma in situ (LCIS)], diagnosed on core needle biopsy (CNB). Retrospective series of pure ALH and LCIS reported "upgrade" rate to DCIS or invasive cancer in 0-40%. Few reports document radiologic/pathologic correlation to exclude cases of discordance that are the likely source of most upgrades, and there is minimal data on outcomes with follow-up imaging and clinical surveillance. METHODS: Cases of LN alone on CNB (2001-2014) were reviewed. CNB yielding LN with other pathologic findings for which surgery was indicated were excluded. All patients had either surgical excision or clinical follow-up with breast imaging. All cases included were subject to radiologic-pathologic correlation after biopsy. RESULTS: 178 cases were identified out of 62213 (0.3%). 115 (65%) patients underwent surgery, and 54 (30%) patients had surveillance for > 12 months (mean = 55 months). Of the patients who underwent surgical excision, 13/115 (11%) were malignant. Eight of these 13 found malignancy at excision when CNB results were considered discordant (5 DCIS, and 3 invasive lobular carcinoma), with the remainder, 5/115 (4%), having a true pathologic upgrade: 3 DCIS, and 2 microinvasive lobular carcinoma. Among 54 patients not having excision, 12/54 (22%) underwent subsequent CNB with only 1 carcinoma found at the initial biopsy site. CONCLUSIONS: Surgical excision of LN yields a low upgrade rate when careful consideration is given to radiologic/pathologic correlation to exclude cases of discordance. Observation with interval breast imaging is a reasonable alternative for most cases.

Invasive mucinous carcinoma of the breast and response patterns after neoadjuvant chemotherapy (NAC).

AIMS: Neoadjuvant chemotherapy (NAC) is often used to treat localised invasive breast cancer. Invasive mucinous carcinoma (IMC) is considered to be an indolent form of invasive breast cancer, and is rarely treated with NAC. We report the largest series of IMCs treated with NAC, and report a characteristic, but not well recognised, pattern of pathological response. METHODS AND RESULTS: Our series included seven patients with IMC treated with NAC. Three patients presented with locally advanced disease, three patients had tumours that were HER-2/neu-positive, and four patients had tumours with admixed mucinous and micropapillary features. Clinical and imaging assessment of response showed persistent and, in some cases, progressive disease, despite evidence of significant pathological response in these cases. Pathological assessment after NAC demonstrated marked reduction in tumour cellularity, but persistent space-occupying mucin pools, showing acellular mucin in one case, <1% tumour cellularity in three cases, and 5-10% cellularity in three cases in both the treated breast and axillary lymph nodes. CONCLUSIONS: Persistent mass-forming low-cellular or acellular mucin pools can result in discordant clinical, imaging and pathological findings in IMC treated with NAC.

MYB rearrangement and immunohistochemical expression in adenomyoepithelioma of the breast: a comparison with adenoid cystic carcinoma.

AIMS: Adenomyoepithelioma (AME) and adenoid cystic carcinoma (ACC) of the breast have been noted to occur simultaneously, raising the possibility that AME may represent a related or precursor lesion to ACC. ACC frequently harbours genetic rearrangement of the MYB gene. We sought to clarify the relationship between AME and ACC by comparing their rates of MYB expression by IHC and MYB rearrangement by FISH. METHODS AND RESULTS: IHC and FISH for MYB rearrangement were performed on paraffin-embedded sections of 11 breast ACCs, 11 non-breast ACCs and 11 breast-AMEs. Using FISH, five of eight (63%) interpretable breast ACCs demonstrated MYB gene rearrangement. Nine of 11 (81%) breast ACCs demonstrated MYB expression (range = 20-95%). Of the three FISH-negative breast ACCs, two were solid variant and demonstrated strong MYB expression by IHC. Of the 10 interpretable non-breast ACCs, six showed MYB rearrangement, all of which were conventional type. Nine of these 11 (81%) cases showed MYB immunoexpression (range = 10-90%), including three solid-variant cases which were negative by FISH. No MYB rearrangements were detected by FISH in 10 interpretable AMEs. However, three of 11 cases (27%) showed weak to moderate MYB expression by IHC (range = 10-40%). CONCLUSIONS: Our results indicate that AMEs do not harbour MYB gene rearrangement. IHC for MYB may be helpful in diagnosing FISH-negative cases of ACC, particularly the diagnostically more difficult solid variants. However, weak to moderate MYB expression in a subset of AMEs highlights not only a potential diagnostic pitfall, but also shared pathophysiology with ACC worth investigating further at the genomic level.

Ultrasound-guided wire localization of focal ductal dilatation in the evaluation and treatment of pathologic nipple discharge.

Patients presenting with pathologic nipple discharge (PND) often pose a diagnostic and therapeutic challenge. We used ultrasound to identify focal ductal dilatation-hypothesized to be a radiographic manifestation of the causative lesion-in patients with PND and no relevant clinical or radiographic findings. Twenty-two excisions guided by ultrasound wire localization of focal duct dilation were performed. Surgical pathology revealed papilloma in 20 cases (91%); atypia or carcinoma was detected in 7 cases (32%). The ultrasound finding of focal duct dilatation enables excision of otherwise occult though clinically significant lesions and is worthy of further study.

Close and Positive Lumpectomy Margins are Associated with Similar Rates of Residual Disease with Additional Surgery.

BACKGROUND: Current guidelines state that "no ink on tumor" constitutes adequate surgical margins for lumpectomy specimens. However, there remains uncertainty when tumor is close (<1 mm) to multiple inked margins. METHODS: All local excisions for invasive breast cancer during 3 years at one center were reviewed. Tumor characteristics, margin status, patient age, reoperations, and pathology of reexcised specimen were recorded. Chi-square analysis and regression models were used to identify factors associated with residual disease upon reoperation. RESULTS: In 533 lumpectomies for invasive cancer, 60 (11 %) had at least one positive margin, and 106 (20 %) had one or more close margin. Multiple margins were either close or positive in 67 cases. Reoperation was performed in 125 of 533 cases (23 %) for close or positive margins. Positive margins were significantly more likely to undergo reoperation compared with close margins (p < 0.001). On reoperation, 73 of 125 (58 %) demonstrated residual cancer, including 39 of 68 (57 %) with close margins, and 34 of 57 (60 %) with positive margins (p = 0.52). When multiple margins were close or positive, residual cancer was found on reexcision in 45 of 59 (76 %) cases as opposed to 34 of 79 (43 %) cases with only one involved margin (p < 0.001). When controlling for other factors, positive margins were no more associated with residual disease than close margins (p = 0.32), whereas multiple close or positive margins were associated with significantly higher risk of residual disease (odds ratio 6.1; p = 0.002; 95 % confidence interval 2.6-14.45). CONCLUSIONS: The only significant predictor of residual tumor was multiple close or positive margins. It may be appropriate to recommend reexcision for patients with multiple close margins.

The clinical significance of internal mammary lymph node (IMLN) biopsy during autologous reconstruction in breast cancer patients.

The clinical significance of IMLN metastases in breast cancer is controversial. Although IMLN status is an integral part of current AJCC staging of breast cancer, the elective sampling of IMLN is not part of routine surgery for breast cancer. The purpose of this study was to determine the incidence of IMLN metastases, associated risk factors if any, and its impact on further management and outcome. We retrospectively studied 470 cases that underwent autologous reconstruction surgery between 2002 and 2014. Of 470 cases, 157 breast cancer cases had histology-confirmed IMLN removal during the reconstruction. Only 9 patients (6 %) showed IMLN metastases as compared to 45 (34 %) that showed axillary nodal metastases (p < 0.01). Interestingly, 4 patients had metastases limited to IMLN without any metastases to axillary nodes. IMLN metastasis was significantly associated with age <40 years, lymphovascular invasion, and negative PR status. IMLN metastasis resulted in upstaging of 2 patients from stage I to III, and 1 from stage II to III. Five patients received additional chest wall radiation to target the positive IMLNs. Nine of 157 (6 %) patients with IMLN removal during reconstruction had loco-regional recurrence/metastasis as compared to 20 of 293 (7 %) patients without IMLN removal (p > 0.05) (follow-up, 1-134 months). The overall rate of IMLN metastases (6 %) is much lower than the rate of axillary node metastases. Selective biopsy of IMLNs in patients with breast cancer, especially if younger than 40 years, and with lymphovascular invasion and negative PR status, may guide adjuvant treatment.

Are cytokeratin-positive cells in sentinel lymph nodes of patients with invasive breast carcinomas up to 5 mm usually insignificant?

AIMS: It is known that sentinel lymph nodes (SLN) may be falsely positive due to displaced epithelial cells, particularly in cases with an underlying intraductal papilloma. Given the low metastatic rate in pT1a carcinomas, we aimed to investigate the effect of this phenomenon on staging. METHODS AND RESULTS: Using morphology and immunohistochemistry, we classified the epithelial cells in the SLN in 39 cases of pT1a carcinoma as positive for carcinoma in six, negative in 26 and undetermined in seven. Comparative morphology and immunohistochemistry (using oestrogen receptor, ER) showed complete concordance between the primary carcinoma and SLN in the positive cases, and discordance in the negative cases. The primary tumours in the negative cases were ER-positive except one, in contrast to the SLN cytokeratin-positive (CK(+) ) cells, which were ER-negative. The exception was a case with a Her2-positive primary, in which the SLN CK(+) cells did not stain for Her2. In these cases considered SLN-negative, either displacement (19 cases) or an intraductal papilloma (20 cases) was identified. Two cases showed displacement of benign and malignant cells in the biopsy. Seven cases were indeterminate due to the small number of SLN CK(+) cells, precluding comparison with the primary. CONCLUSION: Given the low rate of metastases in pT1a carcinomas, the significance of SLN CK(+) cells should be resolved by comparative morphology and immunohistochemistry to prevent erroneous upstaging.

Re-evaluating the role of sentinel lymph node biopsy in microinvasive breast carcinoma.

The role of sentinel lymph node biopsy in microinvasive breast carcinoma is unclear. We examined the incidence of lymph node metastasis in patients with microinvasive carcinoma who underwent surgery at our institution. Retrospective review of our pathology database was performed (1994-2012). Of 7000 patients surgically treated for invasive breast carcinoma, 99 (1%) were classified as microinvasive carcinoma. Axillary staging was performed in 81 patients (64, sentinel lymph node biopsy; 17, axillary lymph node excision). Seven cases (9%) showed isolated tumor/epithelial cells in sentinel nodes. Three of these seven cases showed reactive changes in lymph nodes, papillary lesions in the breast with or without displaced epithelial cells within biopsy site tract, or immunohistochemical (estrogen receptor, progesterone receptor, and HER2) discordance between the primary tumor in the breast and epithelial cells in the lymph node, consistent with iatrogenically transported epithelial cells rather than true metastasis. The remaining four cases included two cases, each with a single cytokeratin-positive cell in the subcapsular sinus detected by immunohistochemistry only, and two cases with isolated tumor cells singly and in small clusters (<20 cells per cross-section) by hematoxylin and eosin and immunohistochemistry. The exact nature of cytokeratin-positive cells in the former two cases could not be determined and might still have represented iatrogenically displaced cells. In the final analysis, only two cases (3%) had isolated tumor cells. Three of these four cases had additional axillary lymph nodes excised, which were all negative for tumor cells. At a median follow-up of 37 months (range 6-199 months), none of these patients had axillary recurrences. Our results show very low incidence of sentinel lymph node involvement (3%), only as isolated tumor cells, in microinvasive carcinoma patients. None of our cases showed micrometastases or macrometastasis. We recommend reassessment of the routine practice of sentinel lymph node biopsy in patients with microinvasive carcinoma.

Breast pathology review: does it make a difference?

BACKGROUND: Breast pathology is a challenging field, and previous work has shown discrepancies in diagnoses, even among experts. We set out to determine whether mandatory pathology review changes the diagnosis or surgical management of breast disease. METHODS: Cases were referred for pathology review after patients presented for surgical opinion to the Dubin Breast Center at Mount Sinai Medical Center over the course of 2 years. Surgical pathologists with expertise in breast disease reviewed slides submitted from the primary institution and rendered a second opinion diagnosis. Comparison of these reports was performed for evaluation of major changes in diagnosis and definitive surgical management. RESULTS: A total of 306 patients with 430 biopsy specimens were reviewed. Change in diagnosis was documented in 72 (17 %) of 430 cases and change in surgical management in 41 (10 %). A change in diagnosis was more likely to occur in patients originally diagnosed with benign rather than malignant disease (31 vs. 7 %, p < 0.001). Twelve (7 %) of 169 specimens initially diagnosed as benign were reclassified as malignant. A malignant diagnosis was changed to benign in 4 (2 %) of 261 cases. Change in diagnosis was less common in specimens originating from commercial laboratories than community hospitals or university hospitals (8, 19, 21 %, p = 0.023). Change in management was not dependent on initial institution. Type of biopsy specimen (surgical or core) did not influence diagnostic or management changes. CONCLUSIONS: We recommend considering breast pathology review based on the individual clinical scenario, regardless of initial pathologic diagnosis or originating institution.

Evolution of sentinel lymph node biopsy in breast cancer, in and out of vogue?

Sentinel lymph node biopsy (SLNB) was introduced 2 decades ago and thereafter validated for routine surgical management of breast cancer, including cases treated with neoadjuvant chemotherapy. As the number of lymph nodes for staging has decreased, pathologists have scrutinized SLN with a combination of standard hematoxylin and eosin, levels, immunohistochemistry (IHC), and molecular methods. An epidemic of small-volume metastases thereby arose, leading to modifications in the American Joint Committee on Cancer staging to accommodate findings such as isolated tumor cells (ITC) and micrometastases. With the goal of determining the significance of these findings, retrospective followed by prospective trials were performed, showing mixed results. The ACOSOG Z10 and NSABP B-32 trials both independently showed that ITC and micrometastases were not significant and thus discouraged the use of levels and IHC for detecting them. However, the Surveillance Epidemiology and End Results database showed that patients with micrometastases had an overall decreased survival. In addition, the MIRROR (Micrometastases and ITC: Relevant and Robust or Rubbish?) trial, showed that patients with ITC and micrometastases treated with adjuvant therapy had lower hazard ratios compared with untreated patients. Subsequently, the ACOSOG Z0011 trial randomized patients with up to 2 positive SLN to axillary lymph node dissection (ALND) or not, all treated with radiation and chemotherapy, showing no difference in survival or recurrence rates between the 2 groups and causing a shift from ALND. As the rate of ALND has declined, the necessity of performing levels, IHC, frozen section, and molecular studies on SLN needs to be revisited.

Breast cancer in male-to-female transsexuals: use of breast imaging for detection.

OBJECTIVE: The purposes of this article are to describe two cases of breast cancer in male-to-female transsexuals and to review eight cases previously reported in the literature. CONCLUSION: Breast cancer occurs in male-to-female transsexuals who receive high doses of exogenous estrogen and develop breast tissue histologically identical to that of a biologically female breast. This exposure to estrogen results in increased risk of breast cancer. The first patient described is a male-to-female transsexual with screening-detected ductal carcinoma in situ and a family history of breast cancer. The other patient is a male-to-female transsexual with invasive ductal carcinoma that was occult on diagnostic digital mammographic and ultrasound findings but visualized on digital breast tomosynthesis and breast MR images. The analysis of the eight previously reported cases showed that breast cancer in male-to-female transsexuals occurs at a younger age and is more frequently estrogen receptor negative than breast cancer in others born biologically male. Screening for breast cancer in male-to-female transsexuals should be undertaken for those with additional risk factors (e.g., family history, BRCA2 mutation, Klinefelter syndrome) and should be available to those who desire screening, preferably in a clinical trial.