Keratin immunohistochemistry does not contribute to correct lymph node staging in patients with invasive lobular carcinoma

The heterogeneity of breast cancer metastasis: a bioinformatics analysis utilizing single-cell RNA sequencing data

PURPOSE

Breast cancer is a common malignancy in women, and its metastasis is a leading cause of cancer-related deaths. Single-cell RNA sequencing (scRNA-seq) can distinguish the molecular characteristics of metastasis and identify predictor genes for patient prognosis. This article explores gene expression in primary breast cancer tumor tissue against metastatic cells in the lymph node and liver using scRNA-seq.

METHODS

Breast cancer scRNA-seq data from the Gene Expression Omnibus were used. The data were processed using R and the Seurat package. The cells were clustered and identified using Metascape. InferCNV is used to analyze the variation in copy number. Differential expression analysis was conducted for the cancer cells using Seurat and was enriched using Metascape.

RESULTS

We identified 18 distinct cell clusters, 6 of which were epithelial. CNV analysis identified significant alterations with duplication of chromosomes 1, 8, and 19. Differential gene analysis resulted in 17 upregulated and 171 downregulated genes for the primary tumor in the primary tumor vs. liver metastasis comparison and 43 upregulated and 4 downregulated genes in the primary tumor in the primary tumor vs lymph node metastasis comparison. Several enriched terms include Ribosome biogenesis, NTP synthesis, Epithelial dedifferentiation, Autophagy, and genes associated with epithelial-to-mesenchymal transitions.

CONCLUSION

No single gene or pathway can clearly explain the mechanisms behind tumor metastasis. Several mechanisms contribute to lymph node and liver metastasis, such as the loss of differentiation, epithelial-to-mesenchymal transition, and autophagy. These findings necessitate further study of metastatic tissue for effective drug development.

Lack of Clinical Value for Immunohistochemistry for Sentinel Lymph Node Assessment in Invasive Lobular Carcinoma

BACKGROUND

The distinct histologic appearance of invasive lobular carcinoma (ILC) may pose diagnostic challenges for sentinel lymph node (SLN) analysis. We evaluated the impact of cytokeratin immunohistochemistry (IHC) on SLN assessment in ILC and its contribution to pathologic nodal upstaging.

METHODS

We identified ILC patients treated with SLN surgery at our institution between September 2008 and August 2021. IHC for SLN assessment was employed at the discretion of the pathologist. Differences between groups evaluated with and without IHC were compared using Chi-square tests.

RESULTS

Overall, 608 cases of ILC were identified in patients who underwent SLN surgery. IHC was used in 301 cases (49.5%) and was not associated with cT category, pT category, or tumor grade. Use of IHC increased detection of SLN+ disease when isolated tumor cells (ITCs) were included in the analysis (35.9% with IHC vs. 21.2% without IHC; p < 0.001). There was no effect on nodal upstaging to micrometastatic disease (pN1mi) or greater (21.9% with IHC vs. 21.2% without IHC; p = 0.82). IHC did not increase the number of positive SLNs detected (median 1 with and without IHC) nor did it increase axillary lymph node dissection (ALND) rates (11.6% with IHC vs. 15.3% without IHC; p = 0.18).

CONCLUSION

IHC improved detection of pN0(i+) disease among ILC patients undergoing SLN surgery. IHC did not increase upstaging to pN1mi or higher categories of nodal disease, detection of a greater number of positive SLNs, or ALND rates. Our data suggest routine use of IHC for SLN assessment in ILC patients does not add clinical utility.

Sentinel Lymph Nodes in Classic Invasive Lobular Carcinoma of the Breast: Cytokeratin Immunostain Ensures Detection, and Precise Determination of Extent, of Involvement

The assessment of sentinel lymph nodes (SLN) on hematoxylin and eosin (H&E)-stained sections in cases of classic type of invasive lobular carcinoma (cILC) is considered unreliable, particularly in cases with minimal involvement, that is by either isolated tumor cells (pN0i+) or micrometastases (pN1mi). Although the impact of minimal SLN involvement has been shown to be insignificant in most clinical trials (even though cILC was either under-represented or not separated in the respective cohorts), the results of MIRROR trial did emphasize the need for additional therapy in cases with minimally involved SLN to ensure improved disease-free survival. We sought to study the role of cytokeratin immunohistochemistry (CK-IHC) in evaluating SLN in cILC. A total of 582 cILC cases with SLN diagnosed over a 12-year period (2005 to 2016) were reviewed. In all, 394/582 (68%) cases had H&E(-)/CK(-) SLN. In total, 188/582 (32%) cases showed some degree of SLN involvement of which 143/582 (25%) cases had readily identifiable SLN involvement on H&E slides. Overall, 45/582 (7.7%) cases had H&E(-)/CK(+) SLN. The following data relate to the latter subset of 45 cases. Mean age of patients: 61 y (range: 32 to 86 y); right: 24 (53%), left: 21 (47%); multifocal and/or multicentric: 22 (49%); mean size: 2.0 cm (range: 0.25 to 4.4 cm); mean number of SLN: 2.5; mean number of involved SLN: 1.2; and cases with prior needle core or excisional biopsy: 45 (100%). CK(+) cells were identified in isolation or in loose clusters, either in subcapsular sinuses or nodal cortex or both. Overall, 30/45 (67%) showed ≤200 CK(+) cells (ie, pN0i+), and 15/45 (33%) showed >200 CK(+) cells (ie, pN1mi). In total, 15/45 (33%) cases underwent axillary lymph node dissection, of which 4/45 (9%) cases were positive. cILC recurred in 3/45 (7%) cases. On statistical analyses, the number of CK(+) cells (≤/>200) did not correlate with either axillary lymph node-positivity or with recurrence. Number of CK(+) cells (≤/>200) readily distinguished pN0i+ from pN1mi based on AJCC's numerical criteria. CK(+) cells could be quantified in linear terms (ie, AJCC's size criteria of pN0i+ and pN1mi was applicable) in only 2 cases. On the basis of these findings, the use of CK-IHC staining should be considered for SLN in cases of cILC to ensure detection, and precise determination of extent, of involvement; however, the prognostic significance of this procedure would have to await results of additional studies with long-term follow-up.

Achieving breast cancer surgery in a single setting with intraoperative frozen section analysis of the sentinel lymph node

BACKGROUND

Current guidelines recommend full axillary lymph node dissection (ALND) whenever the SLN is positive for metastases. In our institute, we aim to complete surgery in a single setting and base the decision for ALND on the intraoperative FS analysis of the SLN. In this study, we evaluate the efficacy this practice in terms of the accuracy of FS analysis, patient recall rate, and additional time required for FS analysis.

MATERIALS AND METHODS

Retrospective review was performed of 586 patients who underwent SLN biopsy at our institution from January 1, 2006 to December 31, 2010. Intraoperative FS analysis was routinely performed in all cases with a preoperative diagnosis of invasive breast cancer and in selected cases of ductal carcinoma in situ according to surgeon preference.

RESULTS

The SLN was positive for metastases in 123 (22.7%) patients; this was identified on FS analysis in 107 patients. FS analysis had a sensitivity of 87.0% and specificity of 100% and resulted in a patient recall rate of 3%. Micrometastasis accounted for most of the false negative FS results. These deposits were mostly detected only on deeper sectioning of the permanent sections of the SLN. An invasive lobular histology and lymphovascular invasion were found to be independent predictors of a false negative FS on multivariate analysis (P < .01). Intraoperative FS did not significantly prolong operating times.

CONCLUSION

Intraoperative FS analysis is an accurate and efficient means of rapid SLN assessment and allows ALND to be completed in a single setting.

Lobular and non-lobular breast cancers differ regarding axillary lymph node metastasis: a cross-sectional study on 4,292 consecutive patients

Invasive lobular carcinoma (ILC) accounts for 8-14% of all breast cancers and carries distinct prognostic and biologic implications. The goal of our study was to investigate the impact of lobular histology on axillary lymph node (ALN) involvement. This is a cross-sectional study of 4,292 consecutive patients surgically treated for breast carcinoma at the University Hospitals Leuven. Logistic regression analysis was used to relate ILC to lymph node involvement while controlling for the following clinicopathologic features: tumor size, multifocal disease, tumor grade, lobular subtype and the combined steroid, and Her-2 status. Odds ratios (ORs) and 95% confidence intervals (CIS) were computed. A subgroup analysis was performed for patients that underwent a sentinel lymph node (SLN) procedure. The observed incidence of ILC was 13%. ILCs were larger, were more often grade II, multifocal, steroid receptor positive and Her-2 negative, and tended to be present in older patients. Incidence of ALN involvement was 42.0% for ILCs versus 38.3% for other tumors (OR 1.17, 95% CI 0.97-1.40). For the SLN subgroup, ILCs were less often ALN positive than non-ILCs (20.5% versus 28.3%, OR 0.66, 95% CI: 0.41-1.00). In the multivariable analysis, the lobular subtype was identified as less likely to have ALN involvement (adjusted OR 0.66, 95% CI 0.53-0.82). The analysis for the SLN subgroup showed comparable results (adjusted OR 0.49, 95% CI 0.30-0.78). This study has demonstrated that the lobular subtype is an independent predictor of lymph node involvement with ILC having a lower incidence of involved lymph nodes. The mildly higher incidence of ALN metastasis in lobular cancers in univariable analysis is not due to the lobular subtype, but due to confounding factors that interact with lymph node involvement.

Accurate classification of sentinel lymph node metastases in patients with lobular breast carcinoma

Among pathologists there is low reproducibility in classifying small volume metastases in sentinel lymph node particularly in cases of invasive lobular carcinoma. We postulate that strict adherence to American Joint Commission on Cancer (AJCC) 2003 criteria may result in inaccurate staging of lobular carcinoma patients. We reviewed cases of metastatic lobular carcinoma in sentinel lymph node biopsies between 1998 and 2008. All sentinel lymph nodes were reassessed using strict adherence to AJCC 2003 criteria. Subsequent axillary lymph node dissection and clinical follow-up were reviewed. Fifty-one patients met our inclusion criteria and were originally classified by the primary pathologist as follows: 10 isolated tumor cells, 8 micrometastases, 27 macrometastases, and 6 'positive' cases without further classification. Cases were re-classified using strict adherence to AJCC 2003 criteria as follows: 21 isolated tumor cells, 2 micrometastases, and 28 macrometastases. Twelve isolated tumor cells cases underwent full axillary dissection, and 3 (25%) had additional macrometastases. All micrometastatic cases underwent axillary dissection; all were negative. Twenty-two macrometastatic cases underwent full axillary dissection and 16 (73%) had additional macrometastases. Diffuse single cells or small clusters should not be interpreted as isolated tumor cells in invasive lobular carcinoma sentinel lymph nodes. The criteria for assessing small volume metastases in the sentinel lymph node of patients with invasive lobular carcinoma need to be more clearly defined.

Comparison of intraoperative frozen section analysis for sentinel lymph node biopsy during breast cancer surgery for invasive lobular carcinoma and invasive ductal carcinoma

BACKGROUND

Sentinel lymph node (SLN) biopsy is the standard of care for the surgical assessment of the axilla during breast cancer surgery. However, the diagnostic accuracy of intraoperative frozen section analysis for confirming metastatic involvement of SLNs in cases of invasive lobular carcinoma (ILC) versus that of invasive ductal carcinoma (IDC) has generated controversy secondary to a frequently low-grade cytologic appearance and an often discohesive pattern displayed by metastatic lymph nodes in ILC. In the current report, we present a comparison of intraoperative frozen section analysis for confirming the presence of metastatic disease within SLNs during breast cancer surgery for ILC and IDC.

METHODS

We evaluated the results of 131 consecutive cases of ILC from 1997 to 2008 and 133 cases of IDC (selected by a random sequence generator program) from amongst 1163 consecutive cases of IDC from the same time period. All cases had at least one SLN that had both intraoperative frozen section analysis and confirmatory permanent section analysis performed.

RESULTS

No statistically significant difference was found in the sensitivity (67% vs. 75%, P = 0.385), specificity (100% vs. 100%), accuracy (86% vs. 92%, P = 0.172), false negative rate (33% vs. 25%, P = 0.385), negative predictive value (81% vs. 89%, P = 0.158), and positive predictive value (100% vs. 100%) for frozen section analysis for confirming the presence of metastatic disease within SLNs during breast cancer surgery for ILC and IDC.

CONCLUSION

Since there was no statistically significant difference in sensitivity, specificity, accuracy, false negative rate, negative predictive value, and positive predictive value between frozen section analysis of SLNs for patients with ILC and IDC, the clinical accuracy of confirming metastatic involvement of SLNs on frozen section analysis for ILC should not be considered inferior to the clinical accuracy for IDC. Therefore, frozen section analysis of all SLNs during breast cancer surgery in patients with ILC should remain the standard of care in order to reduce the risk of the need of a later, separate axillary lymph node dissection.