Expression of luminal and basal cytokeratins in human breast carcinoma

We have examined basal and luminal cell cytokeratin expression in 1944 cases of invasive breast carcinoma, using tissue microarray (TMA) technology, to determine the frequency of expression of each cytokeratin subtype, their relationships and prognostic relevance, if any. Expression was determined by immunocytochemistry staining using antibodies to the luminal cytokeratins (CKs) 7/8, 18 and 19 and the basal markers CK 5/6 and CK 14. Additionally, assessment of alpha-smooth muscle actin (SMA) and oestrogen receptor status (ER) was performed. The vast majority of the cases showed positivity for CK 7/8, 18 and 19 indicating a differentiated glandular phenotype, a finding associated with good prognosis, ER positivity and older patient age. In contrast, basal marker expression was significantly related to poor prognosis, ER negativity and younger patient age. Multivariate analysis showed that CK 5/6 was an independent indicator for relapse free interval. We were able to subgroup the cases into four distinct phenotype categories (pure luminal, mixed luminal/basal, pure basal and null), which had significant differences in relation to the biological features and the clinical course of the disease. Tumours classified as expressing a basal phenotype (the combined luminal plus basal and the pure basal) were in a poor prognostic subgroup, typically ER negative in most cases. These findings provide further evidence that breast cancer has distinct differentiation subclasses that have both biological and clinical relevance.     

Lymphoepithelioma-like carcinoma of breast—evaluation for Epstein-Barr virus–encoded RNA,human papillomavirus,and markers of basal cell differentiation

This is a largest series of 5 cases of lymphoepithelioma-like carcinoma (LEC) of the breast attempting to look at the expression of basal cytokeratins (CKs), human papillomavirus, and Epstein-Barr virus–encoded RNAs in these tumors. Five cases were selected after stringent evaluation of all breast carcinomas showing dense lymphoid infiltration. Histologically, all these tumors showed the typical histology except 1 tumor that showed an unusual granulomatous response. All tumors were negative for estrogen and progesterone receptors and HER2 (triple negative). Three tumors expressed CK5/6 and high-molecular-weight CK, whereas only the case with nodal metastasis expressed CK14. Analysis for in situ hybridization for Epstein-Barr virus–encoded RNAs and human papillomavirus DNA on paraffin-processed tissues was negative in all tumors. All of these patients received adjuvant therapy. One patient with tumor expressing basal marker, CK5/6, had contralateral breast malignancy after a duration of 53 months of treatment completion. The rest were disease free with the follow-up period in the range of 6 to 105 months. The lymphoepithelioma-like carcinoma of breast expressed basal CK profile that is more CK5/6 positive than CK14. Analysis of basal markers within these tumors may help in refining the definition of these tumors and in classifying them into prognostically relevant groups.     

Cytokeratin profiles of male breast cancers

AIMS: The prognostic factors and expression of molecular markers in male breast carcinomas are similar to those in female breast cancers. The identification of distinct cytokeratin (CK) profiles (basal as opposed to luminal cells) helps to identify subsets of tumours with different clinical behaviour. The aim of this study was to investigate CK expression in male breast cancer. METHODS AND RESULTS: Thirty-two cases of male breast cancer were studied. The panel of CKs studied by immunohistochemistry included: 5/6, 14, 17, 18 and 19. Pathological findings and CK expression were analysed in all cases. Histological patterns included ductal carcinoma in situ, invasive ductal carcinoma and mixed patterns. Four cases were positive for CK5/6 and CK14, identifying a basal-like phenotype. CK17 was negative in all but two cases. All cases expressing either CK5/6 or CK14 were invasive carcinomas of high nuclear and histological grade and were also larger compared with the tumours not expressing CK5/6 and CK14. All tumours except three (also negative for CK5/6) expressed CK18 and CK19. The four basal-like tumours were negative for Her-2 expression. CONCLUSIONS: Male breast carcinomas have a basal-like phenotype that is similar in frequency to that of female breast carcinomas. The expression of CK5/6 and CK14 identifies a subset of pathologically aggressive male breast cancers.     

Immunohistochemical characterization of molecular subtypes of invasive breast cancer: a study from North India

In recent years breast cancer has been classified on the basis of its molecular characteristics by gene expression profiling. A similar classification using immunohistochemistry has been identified so that it has a wider application. This study was designed to define the precise prevalence of molecular subtypes of invasive breast carcinoma using immunohistochemistry in patients from north India and to correlate it with known clinical and histological prognostic factors. Based on ER/PR/Her2/neu expression, 100 cases of invasive breast cancer were categorized into: ER+ and ? or PR+ and Her2/neu? (47%), ER+ and?or PR+ and Her2/neu+ (15%), ER? and ? or PR? and Her2/neu+ (Her2/neu overexpressing, 21%), ER?, PR? and Her2/neu? (Triple negative, 17%). All cases demonstrated positivity for the luminal Cytokeratins 8/18. In addition, 10% of these tumours showed expression of the basal markers (CK4/14, CK5/6). Among the 17 triple negative cases, eight cases were positive for one of the basal markers and two cases with basal marker expression were Her2/neu overexpressing. The basal markers showed significant correlations only with histological grade and ER negative status. On the basis of hormone receptor, Her‐2/neu and cytokeratin expressions, distinct subclasses of breast cancer have been identified which show significant differences in relation to histological grade and ER status. Expression of basal markers is needed to define basal‐like breast cancer.     

Keratin expression in breast cancers

Cytokeratin (CK) immunohistochemistry can play an important role in breast carcinoma evaluation. We evaluated the expression of a panel of commonly used CKs in a large cohort of breast cancers and assessed its correlation with other biomarkers and breast cancer subtypes. Expression of CK7, CK8, CK18 and CK19 was observed in more than 90?% of all breast carcinomas in this study, confirming their efficacy in immunohistochemical identification of breast cancer. A combination of CK8 and CK7 gave the highest sensitivity for detection of a minute number of breast cancer cells. Expression of other CKs, including CK5/6, CK14 and CK20, correlated positively with high tumour grade. The expression of CK5/6 and CK14 in a significant number of high-grade tumours raised concern regarding the use of absence of their expression to identify breast carcinoma. For identification of the basal subtype, CK5/6 gave a higher detection rate than CK14. CK20 expression was found more frequently than reported in previous studies, might constitute an indicator of poor prognosis and may be associated with the molecular apocrine subtype. This study highlights the diagnostic and prognostic relevance of the unique CK expression patterns in breast cancer.     

The cytokeratin profile of medullary carcinoma of the breast

AIMS: The cytokeratin (CK) phenotype and vimentin expression of 31 medullary carcinomas was studied using commercially available antibodies on archived material. Comparing the phenotype of typical and atypical tumours and the phenotype of metastases, the biological significance of cytokeratin and vimentin expression in medullary carcinomas of the breast was determined. METHODS AND RESULTS: Antibodies to CK4, CK5 and 6, CK7, CK14, CK8 and 18, CK19, CK20 and to vimentin were used. All the typical and atypical medullary carcinomas and the metastases (10 cases) stained negatively for CK4 and positively for CK8-18 (CAM5.2). Almost all the tumours were CK7 and CK19 positive and CK20 negative. Twelve per cent of the tumours contained CK14. Twenty-five per cent of the typical, 43% of the atypical and 20% of the metastatic medullary carcinomas showed CK5-6 positivity. No association between the cytokeratin-vimentin profile of the tumours and axillary node metastases, tumour size or oestrogen receptor status was found but instability of CK expression was demonstrated by comparing the primary tumours with their metastases. CONCLUSIONS: : Medullary carcinomas of the breast express all the glandular type CKs including CK19 and additionally a proportion of the tumours expresses some of the CKs typical for myoepithelial cells. There was no correlation with prognostic factors.     

p63 correlates with both BRCA1 and cytokeratin 5 in invasive breast carcinomas: further evidence for the pathogenesis of the basal phenotype of breast cancer

AIMS: To study the expression of p63, cytokeratin (CK) 5 and CK8/18 in invasive ductal carcinomas and their relationship with BRCA1 and other pathological and immunohistochemical features of clinical significance. METHODS AND RESULTS: Immunohistochemistry with the antibodies p63, CK5, CK8/18, BRCA1, oestrogen receptor, progesterone receptor, p53, c-erbB-2 and Ki67 was performed in 102 formalin-fixed paraffin-embedded samples of invasive ductal carcinomas. The CK5+ cases were submitted to a double-immunolabelling study with p63. There was a strong relationship between CK5 and p63 expression and both markers were associated with hormonal receptor-negative high-grade carcinomas with high proliferative rate. Furthermore, there was coexpression of CK5 and p63 in neoplastic cells, indicating that p63, like CK5, is a marker of the basal phenotype of breast cancer. There was a strong relationship between reduced expression of BRCA1 with both p63 and CK5 expression as well as an inverse correlation between p63 and CK8/18 expression, suggesting that loss of p63 expression is required for the transition between a basal to a luminal phenotype of breast carcinoma. CONCLUSIONS: Since p63 is thought to be a marker of stem cells and may act as an oncogene, our data support the idea that BRCA1 acts as stem cell regulator.     

Biological and prognostic significance of stratified epithelial cytokeratins in infiltrating ductal breast carcinomas

 The biological significance of the differential expression of cytokeratin (CK) polypeptides in breast carcinomas is unclear. We examined the CK profiles of 101 primary infiltrating ductal breast carcinomas using monoclonal antibodies directed against 11 different CKs and against vimentin. Two major CK phenotypes were distinguished: first, a phenotype expressing only the simple-epithelial CKs 7 (variably), 8, 18 and 19, and secondly, a bimodal phenotype co-expressing significant amounts of one or more of the stratified-epithelial CKs 4, 14 and 17. The vast majority of G1 and G2 carcinomas had the simple-epithelium phenotype, as did a subgroup of G3 carcinomas. Interestingly, the majority (62%) of G3 carcinomas exhibited the bimodal phenotype, with the expression of CKs 4, 14 and 17 being statistically correlated with poor histological differentiation and absence of steroid hormone receptors. The distribution of vimentin only partially overlapped with that of these stratified-epithelial CKs. Prognostic analyses suggested that the presence of CKs 4, 14 and/or 17 was associated with short overall and disease-free survival in subgroups comprising G3, oestrogen-receptor-negative and vimentin-negative tumours. In node-positive tumours the correlation between these CKs and a shorter disease-free interval attained statistical significance (log rank, 0.0096). Thus, abnormal CK profiles in ductal breast carcinomas appear to reflect disturbed regulation of differentiation-related gene expression programmes and may prove to be of clinical value. Received: 26 August 1997 / Accepted: 11 February 1998     

Changes in cytokeratin expression accompany squamous metaplasia of the human respiratory epithelium

Summary To determine the characteristics of metaplastic changes of the nasal respiratory epithelium, the distribution of individual cytokeratins (CKs) was studied immunohistochemically and by two-dimensional gel electrophoresis. The authors define four types of changes of the normal pseudostratified columnar epithelium: (1) transitional pseudostratified epithelium (first unusual CK.: no. 13); (2) stratified columnar epithelium (increased expression of CKs 4 and 13; CKs 7, 8, 18 and 19 reduced); (3) stratified squamous epithelium, non-keratinized (appearance of CK 16); and (4) stratified squamous epithelium, keratinized (expression of CKs 1 and 10, variable CK5 and 14 patterns in basal cells). These phenotypes were found simultaneously within single specimens, resulting in apparent overall variability in the immunohistochemical staining patterns. Spatially, changes in CK expression towards normal parts were not abrupt but rather gradual. Biochemical data confirmed the immunohistochemical findings and added CK 6 to the pattern of altered nasal mucosa. The findings of this study suggest a stem cell metaplasia in the nasal epithelium which is based on its inherent bimodal developmental programme. A gradual loss of normal respiratory epithelial differentiation, as seen by the loss of CKs 7, 8, and 18, was paralleled by the appearance of squamous epithelial type CKs, e.g. the expression of CKs 1, 10 and 13. Basal cell types CKs 5, 14, 17 and 19 were maintained during this process. Implications of these results for general concepts of CK expression in the metaplastic process are discussed.