Typical medullary breast carcinomas have a basal/myoepithelial phenotype

Triple negative breast carcinoma and the basal phenotype: from expression profiling to clinical practice

Triple negative breast carcinomas (TNBCs) are a group of primary breast tumors with aggressive clinical behavior. Most TNBCs possess a basal phenotype (BP) and show varying degrees of basal cytokeratin and myoepithelial marker expression. The importance of recognizing these tumors came to light largely as the result of gene expression profiling studies that categorized breast cancer into 3 major groups. Two of these groups are defined by their respective expression of estrogen receptor and HER2. TNBCs represent a third group and are defined by negativity for hormone receptors and HER2. TNBCs currently lack effective targeted therapies and are frequently resistant to standard chemotherapeutic regimens. These tumors tend to occur in premenopausal women and members of specific ethnic groups and a subset are associated with heritable BRCA1 mutations. For patients with sporadic TNBCs and BP tumors, BRCA1 dysfunction seems to play a major role in the development and progression of disease. The pathologist's role in the diagnosis and characterization of TNBCs and BP tumors is currently being defined as we are acquiring knowledge of the biologic and genetic underpinnings that drive this heterogeneous group of diseases. This review will provide a historical prospective on TNBCs and tumors that express basal cytokeratins and myoepithelial makers. Additionally, we will discuss the molecular biologic, genetic and pathologic aspects of these tumors. Guidelines will be provided on how to best approach the diagnosis of these cases and on what input pathologists should provide clinicians to help develop optimal therapeutic and preventative strategies against this aggressive group of breast cancers.

Distribution and significance of caveolin 2 expression in normal breast and invasive breast cancer: an immunofluorescence and immunohistochemical analysis

BACKGROUND

The aims of this study were to define the distribution of caveolin 2 (CAV2) in frozen and formalin fixed, paraffin embedded (FFPE) normal breast samples and the significance of CAV2 expression in breast cancer.

METHODS

Caveolin 2 distribution in frozen and paraffin-embedded whole tissue sections of normal breast was evaluated using immunohistochemistry and immunofluorescence, in conjunction with antibodies to define luminal epithelial cells (oestrogen receptor and cytokeratin 8/18) and myoepithelial/ basal cells (cytokeratins 14 and 5/6, p63 and smooth muscle actin). CAV2 expression was also immunohistochemically analysed in two independent cohorts of invasive breast carcinomas (n = 245 and n = 418).

RESULTS

In normal breast, CAV2 was expressed in myoepithelial cells, endothelial cells, fibroblasts and adipocytes. Luminal epithelial cells showed no or only negligible staining. CAV2 expression was observed in 9.6% of all breast cancers and was strongly correlated with high histological grade, lack of oestrogen receptor, progesterone receptor and cyclin D1 expression, and positivity for epidermal growth factor receptor, basal markers, p53 expression, and high proliferation index. Furthermore, CAV2 expression was significantly associated with basal-like immunophenotype and proved to be a prognostic factor for breast cancer-specific survival on univariate analysis.

CONCLUSION

Our results demonstrate that CAV2 is preferentially expressed in basal-like cancers and is associated with poor prognosis. Further in vitro studies are required to determine whether CAV2 has oncogenic properties or is only a surrogate marker of basal-like carcinomas.

Molecular profiling in breast cancer

Molecular profiling has provided biological evidence for the heterogeneity of breast cancer through the identification of intrinsic subtypes like Luminal A, Luminal B, HER2+/ER- and basal-like. It has also led to the development of clinically applicable gene expression-based prognostic panels like the Mammaprint and Oncotype Dx. The increasingly sophisticated understanding allowed by this and similar technology promises future individualized therapy.

The phenotypic spectrum of basal-like breast cancers: a critical appraisal

There are 2 well-recognized cell populations lining the mammary duct system: the epithelial cells lining the lumen and the myoepithelial cells surrounding them. The mammary stem cell, a putative third cell type, has not yet been well characterized. It is not established whether the putative stem cell expresses the full complement, a subset, or none of the markers of normal epithelial and/or myoepithelial cells. However, it is likely that they would have distinctive markers of their own; whether these are retained or lost in their neoplastic progeny is unknown. All 3 cell types may theoretically undergo malignant transformation. Until recently, however, nearly all attention has been focused on carcinomas of epithelial derivation/differentiation. The advent of oligonucleotide and cDNA microarrays has facilitated gene expression profiling of breast cancers, revealing molecular subclasses that may be prognostically relevant. One such subclass, the basal-like breast carcinomas, has been found in numerous independent datasets to be associated with a comparatively worse overall and disease-free survival. These cancers show expression of molecules characteristic of the normal myoepithelial cell, such as basal cytokeratins, and reduced expression of estrogen receptor-related and Erb-B2-related genes and proteins. The classifier genes that formed the basis for the delineation of basal-like carcinomas were derived from datasets that were composed predominantly of ductal type cancers. Therefore, the clinical significance of a basal-like gene expression or immunohistochemical profile in the other breast cancer subtypes is presently unknown. Herein, we evaluate in detail the current state of knowledge on the pathologic features of breast carcinomas classified as basal-like by immunohistochemical and/or gene expression profiling criteria, with an emphasis on their full phenotypic spectrum and also previously underemphasized areas of heterogeneity and ambiguity where present. There seems to be a phenotypic and biologic spectrum of basal-like or myoepithelial-type carcinomas, just as there is a wide range among tumors of luminal epithelial derivation/differentiation. It is critical to promote lucid morphologic definitions of the molecular subtypes, if this information is intended for use in targeted therapies and patient management.

Identification of typical medullary breast carcinoma as a genomic sub-group of basal-like carcinomas, a heterogeneous new molecular entity

Introduction

Typical medullary breast carcinoma (MBC) has recently been recognized to be part of the basal-like carcinoma spectrum, a feature in agreement with the high rate of TP53 mutations previously reported in MBCs. The present study was therefore designed to identify phenotypic and genetic alterations that distinguish MBCs from basal-like carcinomas (BLC).

Methods

Expression levels of estrogen receptor (ER), progesterone receptor (PR), ERBB2, TP53, cytokeratins (KRTs) 5/6, 14, 8/18, epidermal growth factor receptor and KIT, as well as TP53 gene sequence and high-density array comparative genomic hybridization (CGH) profiles, were assessed and compared in a series of 33 MBCs and 26 BLCs.

Results

All tumors were negative for ER, PR and ERBB2. KRTs 5/6 were more frequently expressed in MBCs (94%) than in BLCs (56%) (p = 0.0004). TP53 mutations were disclosed in 20/26 MBCs (77%) and 20/24 BLCs (83%). Array CGH analysis showed that a higher number of gains (95 regions) and losses (34 regions) was observed in MBCs than in BLCs (36 regions of gain; 13 regions of losses). In addition, gains of 1q and 8q, and losses of X were found to be common to the two groups, whereas gains of 10p (53% of the cases), 9p (30.8% of the cases) and 16q (25.8% of the cases), and losses of 4p (34.8% of the cases), and amplicons of 1q, 8p, 10p and 12p were the genetic alterations found to characterize MBC.

Conclusion

Our study has revealed that MBCs are part of the basal-like group and share common genomic alterations with BLCs, the most frequent being 1q and 8q gains and X losses; however, MBCs are a distinct entity within the basal-like spectrum, characterized by a higher rate of KRT 5/6 expression, a higher rate of gains and losses than BLCs, recurrent 10p, 9p and 16q gains, 4p losses, and 1q, 8p, 10p and 12p amplicons. Our results thus contribute to a better understanding of the heterogeneity in basal-like breast tumors and provide potential diagnostic tools.

Fine-needle aspiration cytology of medullary breast carcinoma: report of two cases and review of the literature with emphasis on differential diagnosis

Medullary carcinoma is a rare variant of breast carcinoma with a relatively good clinical prognosis as strictly defined. Characteristic features on fine-needle aspiration cytology (FNAC) allow medullary carcinoma to be considered in the cytologic differential diagnosis. We present two FNAC cases with such features, including high cellularity with clusters and single intact malignant cells, bizarre stripped nuclei with prominent nucleoli in a lymphoplasmacytic background, and illustrate one case in liquid-based preparation. Surgical excision revealed that one patient had medullary carcinoma, while the second patient had high-grade infiltrating ductal carcinoma. Breast FNAC samples with syncytial fragments, bizarre nuclei with prominent nucleoli, and a chronic inflammatory infiltrate should raise the possibility of medullary carcinoma. However, the differential diagnosis also includes high-grade ductal carcinoma, lymphoma, or metastasis to breast or intramammary lymph nodes; thus, histopathologic analysis is required for definitive diagnosis.

Demystifying basal-like breast carcinomas

"Basal" breast cancers are dominating the breast research literature at present and pathologists are under increasing pressure to evaluate for such a phenotype by their surgical and oncological colleagues. There is also much confusion about how to assess cancers, which immunohistochemical markers to use, what meaning and benefit this provides, and what the surgeons and oncologists will do with the information. Much remains to be done to answer all these questions but here we try to shed light on some of the issues and suggest what is still to come.

Basal-like grade III invasive ductal carcinoma of the breast: patterns of metastasis and long-term survival

Introduction

Cytokeratin (CK) 14, one of several markers expressed in normal myoepithelial/basal cells, is also expressed in a proportion of breast carcinomas. Previous studies have suggested that expression of such 'basal' markers predicts different biological behaviour, with more frequent lung and brain metastases and poorer prognosis than other carcinomas.

Methods

We performed CK14 immunohistochemistry on 443 grade III invasive ductal carcinomas with extended clinical follow-up (mean 116 months), and we correlated CK14 immunopositivity (basal-like phenotype) with clinicopathological criteria.

Results

Eighty-eight of 443 (20%) tumours showed CK14 expression. CK14-positive tumours were more likely to be oestrogen receptor-negative (p < 0.0001) and axillary node-negative (p = 0.001) than were CK14-negative cases. CK14-positive cases developed less bone and liver metastases (hazard ratio [HR] 0.49, p = 0.01, and HR 0.53, p = 0.035, respectively) but more frequent brain metastases (HR 1.92, p = 0.051). In patients without metastatic disease, disease-free survival in CK14-positive cases was significantly better than in CK14-negative cases (HR 0.65, p = 0.005). In patients with metastatic disease, however, CK14 positivity was associated with a poorer prognosis (HR 1.84, p = 0.001). The overall survival in CK14-positive and -negative patients was similar at 5 years (60% and 59%, respectively), but the long-term survival was better in CK14-positive patients (HR 0.69, p = 0.02).

Conclusion

These results demonstrate that basal-like tumours differ in their biological behaviour from other tumours, with a distinct pattern of metastatic spread. Compared to other grade III tumours, basal-like tumours appear to have a relatively good long-term survival but survival after metastases is poor.

Nectin-4 is a new histological and serological tumor associated marker for breast cancer

Introduction

Breast cancer is a complex and heterogeneous disease at the molecular level. Evolution is difficult to predict according to classical histoclinical prognostic factors. Different studies highlight the importance of large-scale molecular expression analyses to improve taxonomy of breast cancer and prognostic classification. Identification of new molecular markers that refine this taxonomy and improve patient management is a priority in the field of breast cancer research.

Nectins are cell adhesion molecules involved in the regulation of epithelial physiology. We present here Nectin-4/PVRL4 as a new histological and serological tumor associated marker for breast carcinoma.

Methods

Expression of Nectin-4 protein was measured on a panel of 78 primary cells and cell lines from different origins and 57 breast tumors by FACS analysis and immunohistochemistry (IHC), respectively. mRNA expression was measured by quantitative PCR.

Serum Nectin-4 was detected by ELISA and compared with CEA and CA15.3 markers, on panels of 45 sera from healthy donors, 53 sera from patients with non-metastatic breast carcinoma (MBC) at diagnosis, and 182 sera from patients with MBC. Distribution of histological/serological molecular markers and histoclinical parameters were compared using the standard Chi-2 test.

Results

Nectin-4 was not detected in normal breast epithelium. By contrast, Nectin-4 was expressed in 61% of ductal breast carcinoma vs 6% in lobular type. Expression of Nectin-4 strongly correlated with the basal-like markers EGFR, P53, and P-cadherin, and negatively correlated with the luminal-like markers ER, PR and GATA3. All but one ER/PR-negative tumors expressed Nectin-4. The detection of Nectin-4 in serum improves the follow-up of patients with MBC: the association CEA/CA15.3/Nectin-4 allowed to monitor 74% of these patients compared to 67% with the association CEA/CA15.3. Serum Nectin-4 is a marker of disease progression, and levels correlate with the number of metastases (P = 0.038). Serum Nectin-4 is also a marker of therapeutic efficiency and correlates, in 90% of cases, with clinical evolution.

Conclusion

Nectin-4 is a new tumor-associated antigen for breast carcinoma. Nectin-4 is a new bio-marker whose use could help refine breast cancer taxonomy and improve patients' follow-up. Nectin-4 emerges as a potential target for breast cancer immunotherapy.

A mouse model of basal-like breast carcinoma with metaplastic elements

Breast cancers arising in carriers of germline BRCA1 mutations frequently have a basal-like phenotype. Basal-like cancers are characterized by high histological grade, central necrotic areas, foci with metaplastic differentiation, lack of hormone receptor and HER2 (ErbB2) expression, and consistent positivity for basal markers, including CK5/6, CK14, and EGFR. We have used germline manipulation to generate a conditional mouse model of Brca1 deficiency. Transgenic expression of Cre recombinase in the mammary gland of these mice results in deletion of exons encoding the C-terminus of Brca1 and leads to tumour formation when combined with heterozygosity for a p53 mutation. Histologically, these mammary gland tumours were characterized by high histological grade, central necrotic areas, and presence of homologous metaplastic elements. These metaplastic elements consisted of neoplastic spindle cells or squamous cell differentiation in the form of keratin pearls or individual cell keratinization. Immunohistochemical analysis revealed expression of basal-like markers in all cases. The tumour phenotype generated in our mouse model was compared with published data on human basal-like breast carcinomas and also with metaplastic breast cancers with a basal-like phenotype; the comparison showed that we have generated a mouse model of basal-like breast cancer, which should prove useful in testing new and targeted treatments for this type of breast cancer.

Sporadic Invasive Breast Carcinomas With Medullary Features Display a Basal-like Phenotype

It is not clear whether invasive breast carcinomas with medullary features (IBCMFs, atypical medullary carcinomas) constitute a specific phenotype of breast cancer that is of biologic significance. Because medullary features are common in BRCA1-associated carcinomas and these tumors frequently show a basal-like phenotype, we examined whether IBCMFs expressed basal/myoepithelial markers and had a basal-like phenotype. We studied the immunohistochemical expression of 15 markers in tissue microarrays containing samples from 35 IBCMFs and 39 grade 3 invasive ductal carcinomas (IDCG3s) of no special type. In addition, we analyzed EGFR, C-MYC, and CCNE gene amplification by fluorescence in situ hybridization, because the expression of these genes is known to be associated with the basal-like phenotype. We defined the basal-like phenotype according to the criteria of Nielsen et al as being those tumors that were ER/HER2-negative and cytokeratin (CK) 5/6- and/or epidermal growth factor receptor-positive. IBCMFs were more frequently hormone receptor- and HER2-negative, but had greater expression of proliferation markers and p53. In addition, IBCMFs more frequently expressed basal/myoepithelial markers, such as CK5/6 and P-cadherin. A basal-like phenotype was found in 62.9% of IBCMFs but in only 18.9% of IDCG3s. No differences in gene amplification were found between IBCMFs and IDCG3s, although C-MYC amplification was more common in tumors without a basal-like phenotype. The identification of IBCMF as an independent group of tumors could be of clinical significance, given the high incidence of cases with a basal-like phenotype, which is a group of tumors with different prognosis and chemotherapy response from those of IDCG3s of no special type.

Sox2: a possible driver of the basal-like phenotype in sporadic breast cancer

Tumours arising in BRCA1 mutation carriers and sporadic basal-like breast carcinomas have similar phenotypic, immunohistochemical and clinical characteristics. SOX2 is an embryonic transcription factor located at chromosome 3q, a region frequently gained in sporadic basal-like and BRCA1 germline mutated tumours. The aim of the study was to establish whether sox2 expression was related to basal-like sporadic breast tumours. Two hundred and twenty-six sporadic node-negative invasive breast carcinomas were immunohistochemically analysed for oestrogen receptor (ER), progesterone receptor (PR), CK5/6, EGFR, vimentin, HER2, ki67, p53 and sox2 using tissue microarrays. Tumours were considered to have basal-like phenotype if they were ER/HER2-negative and CK5/6 and/or EGFR-positive. Thirty cases of this series (13.7%) displayed a basal-like phenotype. Sox2 expression was observed in 16.7% of cases and was significantly more frequently expressed in basal-like breast carcinomas (43.3% in basal-like, 10.6% in luminal and 13.3% in HER2+ tumours, P<0.001). Moreover, Sox2 showed a statistically significant inverse association with ER and PR (P=0.001 and 0.017, respectively) and direct association with CK5/6, EGFR and vimentin (P=0.022, 0.005 and <0.001, respectively). Sox2 is preferentially expressed in tumours with basal-like phenotype and may play a role in defining their less differentiated/'stem cell' phenotypic characteristics.

Quantitative diffusion-weighted MR imaging in the differential diagnosis of breast lesion

The role of diffusion-weighted magnetic resonance imaging (DWI) to differentiate breast lesions in vivo was evaluated. Sixty women (mean age, 53 years) with 81 breast lesions were enrolled. A coronal echo planar imaging (EPI) sequence sensitised to diffusion (b value=1,000 s/mm(2)) was added to standard MR. The mean diffusivity (MD) was calculated. Differences in MD among cysts, benign lesions and malignant lesions were evaluated, and the sensitivity and specificity of DWI to diagnose malignant and benign lesions were calculated. The diagnosis was 18 cysts, 21 benign and 42 malignant nodules. MD values (mean +/- SD x 10(-3) mm(2)/s) were (1.48 +/- 0.37) for benign lesions, (0.95 +/- 0.18) for malignant lesions and (2.25 +/- 0.26) for cysts. Different MD values characterized different malignant breast lesion types. A MD threshold value of 1.1 x 10(-3) mm(2)/s discriminated malignant breast lesions from benign lesions with a specificity of 81% and sensitivity of 80%. Choosing a cut-off of 1.31 x 10(-3) mm(2)/s (MD of malignant lesions -2 SD), the specificity would be 67% with a sensitivity of 100%. Thus, MD values, related to tumor cellularity, provide reliable information to differentiate malignant breast lesions from benign ones. Quantitative DWI is not time-consuming and can be easily inserted into standard clinical breast MR imaging protocols.

Moesin expression is a marker of basal breast carcinomas

Basal breast cancers (BBCs) have a high risk of metastasis, recurrence and death. Formal subtype definition relies on gene expression but can be approximated by protein expression. New markers are needed to help in the management of the basal subtype of breast cancer. In a previous transcriptional analysis of breast cell lines we found that Moesin expression was a potential basal marker. We show here that Moesin protein expression is a basal marker in breast tumors. In a tissue microarray (TMA) containing 547 sporadic breast cancers, of which 108 were profiled for gene expression, Moesin was expressed in 31% of all tumors and in 82% of the basal tumors. To confirm that Moesin expression remained associated with the basal phenotype in specific types of BBCs, we analyzed Moesin expression in 2 other TMAs containing 40 medullary breast cancers (MBCs) and 27 BRCA1-associated breast cancers (BRCA1-BCs), respectively. Moesin was strongly expressed in MBCs (87%; p = 2.4 x 10(-5)) and in BRCA1-BCs (58%; p = 1.3 x 10(-5)) as compared with non-MBCs and sporadic cases. Moesin-expressing tumors display features of BBCs, such as high proliferation rate, hormone receptors negativity, expression of putative basal/myoepithelial markers (CAV1, CD10, CK5/6, CK14, EGFR, P53, P-cadherin and SMA). Survival analysis showed a reduced specific survival and metastasis-free survival in Moesin-expressing tumors by log-rank test (p(SS) = 0.014 and p(MFS) = 0.014). In multivariate analysis, Moesin expression was nearly an independent prognostic marker of poor outcome as shown by Cox proportional hazard model in patients without lymph node metastasis (p = 0.052, HR = 2.38, CI 95[0.99-5.69]).

Basal phenotype identifies a poor prognostic subgroup of breast cancer of clinical importance

BACKGROUND

Breast cancer is recognised to be a heterogeneous disease with a range of morphological appearances and behaviours. The recently recognised basal phenotype (BP) is associated with poor survival, but the clinical implications of this class of breast cancers remain to be adequately defined.

METHODS

We have examined a well-characterised series of 1872 invasive breast carcinomas with a long term follow-up to assess the clinical significance of BP.

RESULTS

A pragmatic definition of the BP as immunophenotypic evidence of basal cytokeratins CK5/6 and/or CK14 expression was used. These tumours were associated with shorter overall survival and disease-free interval in our series as a whole and in both the lymph node (LN) negative and LN positive subgroups. When stratified by histological grade, BP was of highly significant prognostic value in grade 3 but not in grades 1 or 2 tumours. Similarly, it was associated with poor survival in the moderate group of the Nottingham prognostic Index but not in the other groups. In a subgroup comprising LN negative grade 3 tumours, BP was the most powerful prognostic marker followed only by tumour size, while the other variables were non-significant. Patients with BP were more likely to respond to chemotherapy than those with non-basal tumours.

CONCLUSIONS

Our results provide robust evidence that BP is an important class of breast cancers with a particularly aggressive behaviour in patients with LN negative grade 3 disease. We recommend routine identification of BP in breast cancer and the development of effective adjuvant treatment strategies. These are important observations as these tumours typically lack hormone receptor and HER-2 overexpression limiting the range of relevant adjuvant therapies.

Locoregional relapse and distant metastasis in conservatively managed triple negative early-stage breast cancer

PURPOSE

To determine the prognostic significance of triple negative breast cancers with respect to locoregional relapse and distant metastasis in conservatively managed breast cancer patients.

PATIENTS AND METHODS

A database of conservative managed (conservative surgery followed by radiation) patients, in whom all three markers (estrogen receptor, progesterone receptor, and HER2/neu) were available, was reviewed. Patients were classified as triple negative if they tested negative for all three markers. Of 482 patients with all three markers available, 117 were classified as triple negative.

RESULTS

As of September 2005, with a median follow-up time of 7.9 years, of the 482 patients in the study, there have been 53 in-breast relapses, 10 nodal relapses, 77 distant relapses, and 69 deaths. At 5 years, the triple negative cohort had a poorer distant metastasis-free rate compared with the other subtypes (67% v 82%, respectively; P = .002). Triple negative subtype was an independent predictor of distant metastasis (hazard ratio = 2.14; 95% CI, 1.31 to 3.53; P = .002) and cause-specific survival (hazard ratio = 1.79; 95% CI, 1.03 to 3.22; P = .047). There was no significant difference in local control between the triple negative and other subtypes (83% v 83%, respectively). Of 99 BRCA-tested patients in this cohort, 10 had deleterious mutations in BRCA1, and seven had mutations in BRCA2. Of 10 BRCA1 patients, eight were triple negative, whereas only one of seven BRCA2 patients was triple negative (P < .001).

CONCLUSION

Patients classified as triple negative have a poor prognosis. However, there was no evidence that these patients are at higher risk for local relapse after conservative surgery and radiation. Patients with BRCA1 mutations develop predominantly triple negative tumors.

Vimentin and laminin expression is associated with basal-like phenotype in both sporadic and BRCA1-associated breast carcinomas

AIMS

To determine whether basal-like phenotype and vimentin and/or laminin are related in both sporadic/familial (BRCA1 or BRCA2 mutated) tumours.

METHODS

230 non-familial and 28 hereditary node-negative invasive breast carcinomas were immunohistochemically analysed for oestrogen receptors (ER), progesterone receptors (PR), cytokeratin 5/6 (CK5/6), epidermal growth factor receptors (EGFR), Ki67, p53, vimentin and laminin, using tissue microarrays. Tumours were considered to have basal-like phenotype if they were ER negative and HER2 negative, but positive for CK5/6 and/or EGFR.

RESULTS

In sporadic tumours, vimentin expression was found in 77.8% cases with basal-like phenotype and 15.5% of non-basal cases (p<0.001). In familial cases, vimentin was expressed in 83.3% basal-like cancers and 16.7% of non-basal tumours (p<0.001). Vimentin expression was more frequent in BRCA1 than BRCA2 mutation carriers. Vimentin expressing tumours were associated with poor prognosis (p = 0.012) among patients not receiving adjuvant chemotherapy and showed a trend for local recurrence or visceral but not bone metastasis (p = 0.021). Laminin expression was also related to basal-like phenotype in both sporadic/familial cases (p<0.001 and p = 0.007, respectively), but neither with prognosis nor recurrence pattern in sporadic cancers.

CONCLUSIONS

Vimentin and laminin expression is associated with basal-like phenotype in breast cancer. Expression of vimentin and laminin is characteristic of BRCA1 associated tumours. Since vimentin and laminin staining is widely used by pathologists for diagnostic purposes, thus demonstrating the robustness of their specific antibodies, the immunohistochemical evaluation of these two molecules could be used in identification of basal-like breast tumours in both sporadic/familial cases.

Basal-like breast cancer and the BRCA1 phenotype

Breast cancers arising in germline carriers of BRCA1 mutations have a characteristic phenotype that has been shown in many studies to differentiate BRCA1 tumours from sporadic tumours. Recently, it has become clear that the characteristic phenotype of BRCA1 tumours is due to expression of the basal-like phenotype. We review these phenotypes, the evidence for BRCA1 pathway dysfunction in sporadic basal-like cancers, and discuss the clinical significance of the basal-like phenotype for cancer genetics and treatment.

Pathology and gene expression of hereditary breast tumors associated with BRCA1, BRCA2 and CHEK2 gene mutations

Tumors arising in BRCA1 and BRCA2 mutation carriers appear to have specific pathological and gene expression profiles, which show a high level of concordance. BRCA1 tumors are high-grade, negative for hormone receptors, have a high proliferation rate, and are positive for some cell cycle promoter genes. BRCA2 tumors present a phenotype opposite to BRCA1 tumors but very similar to sporadic tumors, except that BRCA2 overexpress some DNA repair markers such as CHEK2, show high cytoplasmic expression of RAD51, and are negative for HER-2 amplification and expression. Some of these characteristics have also been found in cDNA expression studies, although more analysis are necessary in order to obtain new markers that can be associated with a germ line mutation in BRCA1 or BRCA2. In this way, some studies in normal tissues of BRCA1/2 carriers suggest that differences exist in the level of expression of some genes when compared with noncarriers. Finally, IHC studies in tumors carrying a mutation in CHEK2 are rare and show contradictory results, probably due to the low number of these cases. However, they represent an example showing how different mutations of the same gene may be associated with specific histological subtypes of cancer.

Deconstructing the molecular portrait of basal-like breast cancer

Gene-expression profiling has revealed several molecular subtypes of breast cancer, which differ in their pathobiology and clinical outcomes. Basal-like tumors are a newly recognized subtype of breast cancer, which express genes that are characteristic of basal epithelial cells, such as the basal cytokeratins, and are associated with poor relapse-free and overall survival. However, the genetic and epigenetic alterations that are responsible for the biologically aggressive phenotype of these estrogen receptor-negative and HER2/ErbB2-negative tumors are not well understood, thereby hindering efforts to develop targeted therapies. Here, we focus on new insights into the molecular pathogenesis of basal-like breast cancer and explore how these discoveries might impact the treatment of these poor-prognosis tumors.

Metaplastic breast carcinomas are basal-like tumours

AIMS

Recently, an immunohistochemical panel comprising antibodies against HER2, oestrogen receptor (ER), epidermal growth factor receptor (EGFR) and cytokeratin (CK) 5/6 was reported to identify basal-like breast carcinomas, as defined by cDNA microarrays. Our aim was to analyse a series of metaplastic breast carcinomas (MBCs) using this panel plus two other basal markers (CK14 and p63) and progesterone receptor (PR), to define how frequently MBCs show a basal-like immunophenotype.

METHODS AND RESULTS

Sixty-five cases were retrieved from the pathology archives of the authors' institutions and reviewed by three of the authors. Immunohistochemistry with antibodies for HER2, ER, EGFR, CK5/6, CK14 and p63 was performed according to standard methods. All but six cases (91%) showed the typical immunoprofile of basal-like tumours (ER- and HER2-, EGFR+ and/or CK5/6+). When CK14 and p63 were added to the panel, two additional cases could be classified as basal-like. The majority of MBCs lacked PR, except 4/19 (21%) carcinomas with squamous metaplasia.

CONCLUSIONS

Our results demonstrate that MBCs show a basal-like phenotype, regardless of the type of metaplastic elements. Moreover, as these neoplasms frequently overexpress EGFR (57%), patients with MBC may benefit from treatment with anti-EGFR drugs.

Diagnostik und Immunhistochemie des medullären Mammakarzinoms

Medullary carcinoma of the breast has a relatively favorable prognosis despite its malignant histopathological appearance, providing a challenge for the pathologically based diagnosis of breast cancer. Macroscopic and microscopic findings combined provide diagnostic criteria. The importance of the immunophenotype of medullary carcinoma is not well defined. Because the reproducibility of morphological criteria is limited, we conducted an immunohistochemical study in search of markers that could facilitate histopathological classification. We examined 32 medullary carcinomas in comparison with 30 high grade ductal invasive carcinomas with similar morphology using 23 different immunohistochemical markers. The results showed an overlap with the so called basal like subtype of invasive breast cancer (negativity for steroid hormone receptor, positivity for basal cytokeratins). None of the immunohistochemical markers enabled a specific discrimination between the two groups. Medullary carcinomas overexpress EGF-R more frequently (P<0.004). In combining the characteristic morphological criteria and the immunohistochemical detection of the basal like phenotype and EGFR, a higher diagnostic accuracy can be achieved. The immunophenotype alone does not allow a definite classification of medullary carcinoma.

Proteomics of breast cancer: principles and potential clinical applications

Progresses in screening, early diagnosis, prediction of aggressiveness and of therapeutic response or toxicity, and identification of new targets for therapeutic will improve survival of breast cancer. These progresses will likely be accelerated by the new proteomic techniques. In this review, we describe the different techniques currently applied to clinical samples of breast cancer and the most important results obtained with the two most popular proteomic approaches in translational research (tissue microarrays and SELDI-TOF).

Prognostic significance of basal-like phenotype and fascin expression in node-negative invasive breast carcinomas

PURPOSE

Basal-like phenotype tumors are frequently found among BRCA1 germ-line mutated breast carcinomas. They are biologically aggressive and have a tendency towards visceral metastasis when untreated. Nevertheless, it has been suggested that they respond to chemotherapy better than other types of tumors. Fascin expression has been associated with lung metastasis in breast cancer. The aim of this study was to determine whether basal-like phenotype and fascin were related in both sporadic and familial tumors and with prognosis in node-negative sporadic breast cancers.

EXPERIMENTAL DESIGN

230 nonfamilial and 28 hereditary node-negative invasive breast carcinomas were immunohistochemically analyzed using tissue microarrays. Tumors that were estrogen receptor/HER2 negative and cytokeratin 5/6 and/or epidermal growth factor receptor positive were considered to have a basal-like phenotype.

RESULTS

A basal-like phenotype was found in 11.9% of sporadic cancers. Among patients not receiving adjuvant chemotherapy, a basal-like phenotype was associated with poor prognosis (P = 0.001, log-rank test) whereas no such association was found in patients receiving it. Tumors with a basal-like phenotype showed local recurrence (17.4%) or visceral metastasis (13%) but not bone metastasis (P = 0.001). Fascin expression was observed in 25.1% of sporadic invasive breast carcinomas and was associated with the basal-like phenotype, but not with prognosis or recurrence pattern. Fascin was expressed in 83.3% and 16.7% BRCA1- and BRCA2-associated carcinomas, respectively (P = 0.048).

CONCLUSIONS

Basal-like tumors had a tendency towards visceral metastasis and their prognosis was dependent on the use of postoperative chemotherapy. Although fascin expression was associated with the basal-like phenotype, it was not associated with their metastatic behavior. Fascin expression is frequent in BRCA1-associated tumors.

Gene expression profiling shows medullary breast cancer is a subgroup of basal breast cancers

Medullary breast cancer (MBC) is a rare but enigmatic pathologic type of breast cancer. Despite features of aggressiveness, MBC is associated with a favorable prognosis. Morphologic diagnosis remains difficult in many cases. Very little is known about the molecular alterations involved in MBC. Notably, it is not clear whether MBC and ductal breast cancer (DBC) represent molecularly distinct entities and what genes/proteins might account for their differences. Using whole-genome oligonucleotide microarrays, we compared gene expression profiles of 22 MBCs and 44 grade III DBCs. We show that MBCs are less heterogeneous than DBCs. Whereas different molecular subtypes (luminal A, luminal B, basal, ERBB2-overexpressing, and normal-like) exist in DBCs, 95% MBCs display a basal profile, similar to that of basal DBCs. Supervised analysis identified gene expression signatures that discriminated MBCs from DBCs. Discriminator genes are associated with various cellular processes related to MBC features, in particular immune reaction and apoptosis. As compared with MBCs, basal DBCs overexpress genes involved in smooth muscle cell differentiation, suggesting that MBCs are a distinct subgroup of basal breast cancer with limited myoepithelial differentiation. Finally, MBCs overexpress a series of genes located on the 12p13 and 6p21 chromosomal regions known to contain pluripotency genes. Our results contribute to a better understanding of MBC and of mammary oncogenesis in general.

Caveolin-1 expression is associated with a basal-like phenotype in sporadic and hereditary breast cancer

The role of caveolin 1 (CAV1), a structural component of caveolae in breast cancer is controversial, although most studies suggest that it functions as a tumor-suppressor gene. In addition, some studies have identified CAV1 as a marker of myoepithelial cells. Since myoepithelial markers are frequently expressed in breast carcinomas with a basal-like phenotype, which are frequently occurring tumors in women with BRCA1 germline mutations, we evaluated whether CAV1 was associated with a basal-like phenotype in 509 sporadic and 47 hereditary BRCA1-/BRCA2-associated carcinomas. Immunohistochemistry was performed on tissue microarrays and cases were classified as having a basal-like-phenotype if they were estrogen-receptor- and HER2-negative but cytokeratin 5/6- and/or epidermal growth factor receptor-positive. In sporadic carcinomas, CAV1 expression was found in 21 out of 496 valuable cases (4.2%). A basal-like-phenotype was found in 53 out of 498 (10.6%) cases. A strong association was found between CAV1 expression and a basal-like-phenotype, since 52% of tumors that expressed CAV1 had this phenotype, compared with only 9% of CAV1-negative carcinomas (p<0.001). CAV1 was expressed in six (12.8%) familial cases, five of which had a basal-like-phenotype (p = 0.009). Moreover, these six CAV1-positive cases were BRCA1 tumors. The difference in the frequency of CAV1 expression between BRCA1- and BRCA2-associated tumors was statistically significant (p = 0.024). In conclusion, this study reports for the first time CAV1 expression in BRCA1 and BRCA2 hereditary breast cancer and identifies CAV1 as a marker associated with a basal-like-phenotype in both hereditary and sporadic breast cancer.