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.     

P-cadherin and cytokeratin 5: useful adjunct markers to distinguish basal-like ductal carcinomas in situ

Gene expression profiles of invasive breast carcinomas have identified a subgroup of tumours with worse prognosis, which have been called "basal-like". These are characterized by a specific pattern of expression, being estrogen receptor (ER) and HER2 negative, and frequently expressing at least one basal marker such as basal cytokeratins or epidermal growth factor receptor (EGFR). Previously, our group characterized basal-like tumours in a series of invasive breast carcinomas using P-cadherin (P-CD), p63 and cytokeratin 5 (CK5). Based on that study, we hypothesized that those high-grade basal-like invasive carcinomas might have a pre-invasive counterpart, which could be identified using the same approach. A series of 79 ductal carcinomas in situ (DCIS) were classified into distinct subgroups according to their ER, HER2 and basal markers expression. Luminal DCIS expressed ER and constituted 64.6% of the series; the HER2 overexpressing tumours did not express ER and represented 25.3% of the cases, whereas 10.1% lack the expression of ER and HER2 and expressed at least one basal marker (P-CD, CK5, CK14, p63, vimentin and/or EGFR). These basal-like DCIS were mostly high-grade, with comedo-type necrosis, and consistently showed expression of P-CD and CK5. In conclusion, DCIS with a basal-like phenotype represent a small percentage in our series, being P-CD and CK5, the most useful adjunct markers to distinguish this subset of carcinomas in situ of the breast.     

p63, cytokeratin 5, and P-cadherin: three molecular markers to distinguish basal phenotype in breast carcinomas

Human breast carcinomas represent a heterogeneous group of tumors diverse in behavior, outcome, and response to therapy. However, the current system of pathological classification does not take into account biologic determinants of prognosis. The purpose of this study was to classify and characterize breast carcinomas based on variations in protein expression patterns derived from immunohistochemical analyses on tissue microarrays (TMAs). Therefore, 11 TMAs representing 168 invasive breast carcinomas were constructed. Breast tumors were classified into four different subtypes depending on estrogen receptor (ER) and HER2 expression. Basal-type tumors expressed neither of these proteins and represented 7.6% of our series; basal-like HER2-overexpressing tumors did not express ER and represented 17.7%; luminal-type tumors expressed ER and represented 72.8% of this series (luminal A 56.3%, luminal B 16.5%). Moreover, we characterized each subtype based on P-cadherin (P-CD), p63, cytokeratin (CK)5, BCL2, and Ki67 expression. Basal-type tumors were mostly grade III, more frequently P-CD-, p63-, and CK5-positive, and had a high proliferation rate. Conversely, luminal-type tumors rarely expressed basal markers and had a low grade and proliferation rate. Basal-like HER2-overexpressing tumors showed a basal-type profile similar with a high grade and up-regulation of P-CD and CK5. With this study, we show that P-CD, p63, and CK5 are important molecular markers that can be used to distinguish a basal phenotype. In addition, we also demonstrate the usefulness of TMAs in breast carcinoma immunoprofiling.     

Apoptosis occurs more frequently in intraductal carcinoma than in infiltrating duct carcinoma of human breast cancer and correlates with altered p53 expression: detected by terminal-deoxynucleotidyl-transferase-mediated dUTP-FITC nick end labelling (TUNEL)

 

Aims:

We examined the relationship between apoptosis and three different major stages of human breast carcinoma: intraductal carcinoma (DCIS), infiltrating duct carcinoma (IDC) and metastatic carcinoma in lymph nodes. We also determined the correlation between apoptosis and oestrogen receptor (ER), progesterone receptor (PR) and p53.  

Methods and results:

The study investigates the extent of apoptosis in 63 breast carcinomas by in-situ end-labelling, in formalin-fixed, paraffin-processed tissue sections. The 63 breast carcinomas, included 22 DCISs, 26 IDCs, three infiltrating lobular carcinomas (ILC) and 12 metastatic lymph nodes. The apoptotic labelling index was higher in DCIS than IDC and metastatic carcinoma ( P  < 0.001, P  < 0.007, respectively). By immunohistochemistry, we also analysed p53, ER and PR. Apoptosis correlated significantly with p53 ( r  = 0.748, P  = 0.0004) in IDC. Also, ER correlated significantly with PR ( r  = 0.629, P  = 0.00001). No apparent correlation was found between the apoptosis and ER or PR.  

Conclusion:

Our data suggest that not only does apoptosis differ between intraductal carcinoma and infiltrating carcinoma but also it might be regulated by altered p53 expression.     

Hormone receptor status and HER2/neu overexpression determined by automated immunostainer on routinely fixed cytologic specimens from breast carcinoma: correlation with histologic sections determinations and diagnostic pitfalls

Although fine-needle aspiration cytology is a routine procedure for the diagnosis of breast carcinoma, cytologic specimens have rarely been used for evaluation of hormone receptor status and HER2/neu overexpression. In order to compare the biological markers on cytology and on histology, routinely fixed smears of 110 primary breast carcinomas were immunostained for estrogen receptor (ER), progesterone receptor (PgR), and HER2/neu by automated immunostainer and the results were compared with the corresponding histologic sections. ER was expressed in 76 of 110 (69%) cases and PgR was expressed in 51 of 110 (46%). Overexpression of HER2/neu was observed in 30 of 110 (27%) cases. Concordance between cytology and histology was 98% for ER, 95% for PgR, and 100% for HER2/neu. There was no false positive result on smears. Diagnostic pitfalls in determination of hormone receptor status on smears included intratumoral heterogeneity and presence of mucin.     

p16INK4a expression in basal-like breast carcinoma

BLBC represents a distinctive group of invasive breast carcinomas with specific genotype and immunopro-file. BLBC is usually defined by gene expression profiling and is currently associated with poor outcome. BLBCs are estrogen receptor (ER) negative, progesterone receptor (PgR) negative, HER2 negative, and usually show a variable expression of basal cytokeratins (CKs), EGFR and CD117. p16 ^INK4a is a tumor suppressor protein, encoded by the CDKN2A gene, which regulates cell cycle. The reported association of abnormalities in the p16/Rb pathway with increased risk of malignancy prompted us to determine the expression of p16^INK4a in a group of BLBC; the results were compared with a group of high-grade invasive carcinoma (HG-IC) of breast. Tissue microarrays (TMA) were constructed in triplicate including 18 BLBC and 18 HG-IC. All BLBC cases were ER-/PgR-/HER2-. Seventeen (94%) BLBC were CK 5/6+/CK 14+; 14 (78%) BLCB showed EGFR expression and 13 (72%) were CD117 positive. BLBCs showed a strong positive reaction with p16 ^INK4a antibody in 16 of 18 (89%) cases. Although the significance of p16 ^INK4a expression in breast cancer is not fully understood, we have shown that p16^INK4a is strongly expressed in breast cancers with basal-like phenotype. Since it is known that p16^INK4a is associated with aggressive behavior in human carcinomas, these data suggest that p16^INK4a play a role in the poor prognosis of BLBC.     

Are bilateral breast cancers and breast cancers coexisting with ovarian cancer different from solitary tumors? A pair‐matched immunohistochemical analysis aimed at intrinsic tumor phenotype

Patients with bilateral breast cancer (BBC) and breast‐ovarian cancer syndrome (BOCS) constitute populations potentially enriched for molecular defects involved in the pathomechanisms of these malignancies. The aim of our study was to compare tumor morphology and expression of estrogen and progesterone receptor, HER2, Ki67, cytokeratin 5/6, E‐cadherin, vimentin and epidermal growth factor receptor in tissue microarrays from 199 tumors from BBC or BOCS patients and 199 age‐matched solitary tumors. Compared to controls, BBC and BOCS considered jointly had lower incidence of DCIS, lower expression of PgR and HER2, and higher expression of Ki67 and vimentin. BOCS tumors were of higher grade, had lower expression of ER and PgR and higher expression of Ki67, CK5/6, vimentin and EGFR. BBC had less DCIS component, lower HER2 expression and higher Ki67 expression. Metachronous BBC (mBBC) had lower expression of ER, PgR and HER2, and higher expression of Ki67 and vimentin. Synchronous BBC (sBBC) had less DCIS component, higher expression of ER, and lower expression of CK5/6, EGFR and E‐cadherin. BBC and breast cancers in BOCS differ in many aspects from solitary tumors. BBC are a heterogeneous group of tumors, differing between sBBC and mBBC. mBBC phenotype shares many features with BOCS tumors.     

Phenotypic evaluation of the basal-like subtype of invasive breast carcinoma.

Microarray profiling of invasive breast carcinomas has identified five distinct subtypes of tumors (luminal A, luminal B, normal breast-like, HER2 overexpressing, and basal-like) that are associated with different clinical outcomes. The basal-like subtype is associated with poor clinical outcomes and is the subtype observed in BRCA1-related breast cancers. The aim of this study was to characterize the histologic and immunophenotypic properties of breast basal-like carcinomas that were first positively identified using DNA microarray analysis. Detailed histologic review was performed on 56 tumors with known microarray profiles (23 basal-like, 23 luminal, and 12 HER2+). Immunohistochemistry for estrogen receptor (ER), HER2, EGFR, smooth muscle actin (SMA), p63, CD10, cytokeratin 5/6, cytokeratin 8/18, and vimentin was performed on 18 basal-like, 16 luminal, and 12 HER2+ tumors. The basal-like tumors were grade 3 ductal/NOS (21/23) or metaplastic (2/23) carcinomas that frequently showed geographic necrosis (17/23), a pushing border of invasion (14/23), and a stromal lymphocytic response (13/23). Most basal-like tumors showed immunoreactivity for vimentin (17/18), luminal cytokeratin 8/18 (15/18), EGFR (13/18), and cytokeratin 5/6 (11/18), while positivity for the myoepithelial markers SMA (4/18), p63 (4/18) and CD10 (2/18) was infrequent. All basal-like tumors tested were ER- and HER2-. Morphologic features significantly associated with the basal-like subtype included markedly elevated mitotic count (P<0.0001), geographic tumor necrosis (P=0.0003), pushing margin of invasion (P=0.0001), and stromal lymphocytic response (P=0.01). The most consistent immunophenotype seen in the basal-like tumors was negativity for ER and HER2, and positivity for vimentin, EGFR, cytokeratin 8/18, and cytokeratin 5/6. The infrequent expression of myoepithelial markers in basal-like carcinomas does not support a direct myoepithelial cell derivation of these tumors. These findings should further assist in the identification of basal-like carcinomas in clinical specimens, facilitating treatment and epidemiologic studies of this tumor subtype.     

Breast cancer in the elderly: a histological assessment

Aims:  To understand the correlation between the expression status of different biological markers in breast cancers in the elderly.
Methods and results:  Three hundred and ninety-seven cases were evaluated for expression of hormone receptors [oestrogen receptors (ER) α and β, progesterone receptor (PR)], basal markers [p63, cytokeratin (CK) 5/6 and CK14] and others (HER2/neu, synaptophysin and chromogranin). The expression rates were 60, 29, 25, 6, 14, 8, 28, 17 and 5%, respectively, for these markers. The expression of ER α and β, PR, synaptophysin and chromogranin at any level correlated with low nuclear or tumour grades, whereas the expression of HER2/neu, CK5/6 and CK14 at any level correlated with high nuclear grade. By using hierarchical clustering, groups of HER2, luminal and basal types were identified. In addition, a neuroendocrine group was also identified, being characterized by expression of synaptophysin, chromogranin, ER and PR, but not HER2/neu, and other basal cytokeratins. This group was associated with lower nuclear grade, and hence better prognosis.
Conclusions:  Breast cancer in the elderly shows similar molecular groupings as other breast cancers, with an additional neuroendocrine group that is associated with a favourable biological marker profile.     

Coordinated expression of ER, PR and HER2 define different prognostic subtypes among poorly differentiated breast carcinomas

Aims:  Histological grade is one of the most important prognostic factors in breast carcinomas, but poorly differentiated neoplasms still have quite heterogeneous biological behaviour, since they can be genetically classified as basal-like, HER2+ or even luminal. The aim was to analyse the frequency of oestrogen receptor (ER), progesterone receptor (PR) and HER2 expression profiles among breast carcinomas with <10% tubular formation, and their correlation with classic prognostic factors.
Methods and results:  One hundred and thirty-four samples of paraffin-embedded tumours were studied retrospectively. The tumours were classified in to four groups by their ER/PR/HER2 profile: (i) ER+ and/or PR+ but HER2−; (ii) ER+ and/or PR+ and HER2+; (iii) ER− and/or PR− but HER2+; and (iv) ER−, PR− and HER2− (triple-negative). The histological features of triple-negative and HER2+ carcinomas overlap. The only difference was the expression of basal cytokeratins (basal CK), which was more frequent among triple-negative carcinomas. Basal-CK expression defined a more aggressive group of tumours, according to the pathological features, regardless of the immunohistochemical profile.
Conclusions:  Group 1 and 2 tumours (ER+ and/or PR+ tumours with or without HER2 expression) were not statistically different, suggesting that poorly differentiated carcinomas with hormone receptors correspond to the luminal B type of tumour. Among poorly differentiated breast carcinomas, the classic profile associated with basal-CK identifies distinct subtypes equivalent to those seen by genetic classification.     

Immunohistochemical study of metaplastic carcinoma and central acellular carcinoma of the breast: central acellular carcinoma is related to metaplastic carcinoma

Metaplastic breast cancers (MBCs) [spindle cell carcinoma (SpCC), squamous cell carcinoma (SCC), and matrix-producing carcinoma (MPC)] and invasive carcinomas with central acellular zones (CACs) were analyzed with respect to biological potential by immunohistochemical analyses. Specimens from 40 patients [20 with MBCs (7 with SCC, 6 with SpCC, 5 with MPC, and 2 with mixed type)] and 20 with CACs were analyzed using antibodies to cytokeratin (CK) 8, 5/6, 14, AE1/AE3, 34αE12, involucrin, c-kit, vimentin (VIM), alpha-smooth muscle actin, p63, epidermal growth factor receptor, epithelial cell adhesion molecule, and estrogen receptor (ER)/progesterone receptor (PR)/HER2. Expression of CK5/6, 34βE12, VIM, nuclear p63, and cytoplasmic p63 was significantly higher with MBCs than CACs (38%/13%, 70%/43%, 85%/33%, 68%/40%, and 48%/18%, respectively). Other markers were expressed at various levels in these tumors, but the difference between them was not significant. Eighteen MBC and 8 CAC cases were triple (ER/PR/HER2) negative; 17 MBCs and 7 CACs were basal-like tumors. Several differences were seen in MBCs and CACs, but they were heterogeneous, differentiating multipotentially into mesenchymal, myoepithelial, basal-like phenotypes with "stem cell-like" features. Thus, CACs are related to MBCs by immunohistochemical analyses as well as according to morphological findings.     

Mesothelial markers in high-grade breast carcinoma

Duhig E E, Kalpakos L, Yang I A & Clarke B E
(2011) Histopathology 59 , 957–964 Mesothelial markers in high‐grade breast carcinoma Aims: Advances in molecular profiling have subdivided breast carcinomas into distinct subtypes. Basal carcinomas are generally oestrogen receptor (ER)?progesterone receptor (PR)?/human epidermal growth factor receptor 2 (HER2)?, and cytokeratin (CK)5/6+. This profile overlaps with that of mesothelial cells. This study of high‐grade breast carcinomas was undertaken to determine the expression of mesothelial markers. Methods and results: Immunohistochemistry was performed on 23 basal‐like breast carcinomas and 30 high‐grade breast carcinomas with variable ER, PR and HER2 expression. The incidence of staining of CK5/6, CK14, calretinin, Wilms’ tumour 1 (WT1), thrombomodulin and epithelial membrane antigen was assessed statistically. CK14 staining was more specifically associated with triple‐negative tumours than CK5/6. Calretinin positivity was statistically associated with basal‐like carcinomas. WT1 and thrombomodulin expression was infrequent and limited to a small number of non‐basal carcinomas. Conclusions: There is an overlap between the immunophenotype of mesothelial cells and that of basal‐like carcinomas of breast. Positive calretinin and CK5/6 are not specific, and may be seen in both mesothelial cells and basal‐like breast carcinomas. Negative ER and PR of basal carcinomas may also bias the observer against a breast origin. However, other negative mesothelial markers, such as WT1 and thrombomodulin, may help point to the correct diagnosis.     

Assessment of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status in the fine needle aspirates of metastatic breast carcinomas

The assessment of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor (HER2) status in the fine needle aspirates of metastatic breast carcinomas has prognostic and therapeutic implications. In this study, expression of ER, PR, and HER2 was assessed by immunohistochemical study in 70 cases of metastatic breast carcinomas and HER2 gene amplification was further evaluated by fluorescence in situ hybridization (FISH) in 38 (54%) cases. Positive expression of ER and PR was seen in 42 (60%) and 16 (23%) cases of metastatic breast carcinomas, respectively. HER2 immunoreactivity was scored as 0/1+ in 39 (56%), 2+ in 10 (14%), and 3+ in 21 (30%) cases. HER2 gene amplification was seen in 20% of HER2 2+ and 64% of HER2 3+ cases. ER, PR, and HER2 status in primary breast cancers were available to comparison in 31 cases (44%). The concordance rates between metastatic and primary breast carcinomas were 81% for ER, 65% for PR and 71% for HER2. Our study demonstrates that ER, PR, and HER2 status can be assessed in the fine needle aspirates of metastatic breast carcinomas and ER has a higher concordance rate between metastatic and primary breast carcinomas than PR and HER2. The addition of HER2 gene amplification FISH test helps in accurate assessment of HER2 status in metastatic breast carcinomas.     

Distribution of p63, cytokeratins 5/6 and cytokeratin 14 in 51 normal and 400 neoplastic human tissue samples using TARP-4 multi-tumor tissue microarray

p63, cytokeratin (CK) 5/6 and CK 14 have been employed in diagnostic pathology as markers of basal, squamous and myoepithelial differentiation in several types of human neoplasms; however, there is scant data on the concurrent expression of these markers in large series of human neoplasms. We analyzed the distribution of these three immunohistochemical markers in 51 normal human tissue samples, 350 carcinomas, 25 malignant melanomas (MMs), and 25 glioblastomas using three serial sections of tissue array research program (TARP)-4 multi-tumor tissue microarray. Also, we performed double immunostainings to characterize the differential distribution of p63/CK 5/6 and p63/CK 14 in normal breast, salivary gland and skin. p63, CK 5/6 and CK 14 were expressed in basal cells of the prostate and respiratory epithelia and in breast and bronchial myoepithelial cells. p63 was also expressed in cytotrophoblast cells of human placenta and in scattered cells of lymph node germinal center. CK 5/6 and CK 14 also stained the cytoplasm of basal cells of esophageal stratified squamous epithelium and transitional epithelial cells of the bladder. No mesenchymal, neural, endothelial, smooth muscle or adipose cells were stained by any of the markers. p63, CK 5/6, and CK 14 were respectively expressed in 92.6%, 75.0%, and 52.9% of the squamous cell carcinomas of the lung, 10.2%, 20.0%, and 7.4% of the ductal carcinomas of the breast, 12.9%, 34.4%, and 11.8% of the serous and 25.0%, 0%, and 0% of the endometrioid carcinomas of the ovary. Lung, prostate and colonic adenocarcinomas, as well as MMs and glioblastomas were only rarely decorated by one of the markers. Only matched samples of 16 squamous cell carcinomas and two ductal carcinomas of the breast co-expressed these three markers. In double immunostainings, p63-CK 5/6, as well as p63-CK 14 were co-expressed by basal/myoepithelial cells of the salivary glands and basal cells of the epidermis. Our results demonstrate that p63, CK 5/6 and CK 14 may be used together in immunohistochemical panels to characterize squamous differentiation in poorly differentiated carcinomas or carcinomas of unknown origin.     

Mixed micropapillary–ductal carcinomas of the breast: a genomic and immunohistochemical analysis of morphologically distinct components

Micropapillary carcinomas (MPCs) can present as a rare histological special type of breast cancer; however, this histological type is more frequently found admixed with invasive ductal carcinomas of no special type (IDC‐NSTs). We have previously demonstrated that pure MPCs constitute a distinct entity at the morphological and genetic levels. Here, we sought to determine whether mixed MPCs have genomic aberrations similar to those found in pure MPCs, and to investigate whether the distinct morphological components of MPCs harbour different genetic aberrations. Using high‐resolution microarray comparative genomic hybridization (aCGH), we profiled a series of 10 MPCs of mixed histology and 20 IDC‐NSTs matched for grade and oestrogen receptor (ER) status. In addition, we generated tissue microarrays containing a series of 24 pure and 40 mixed MPCs and performed immunohistochemical analysis with ER, progesterone receptor (PR), Ki‐67, HER2, cytokeratin (CK) 5/6, CK14, CK17, EGFR, topoisomerase‐IIα, cyclin D1, caveolin‐1 and E‐cadherin antibodies. In situ hybridization was employed to evaluate the prevalence of HER2, TOP2A, EGFR, CCND1, MYC and FGFR1 gene amplification. Our results demonstrate that mixed MPCs harbour similar patterns of genomic aberrations and phenotype (82.5% luminal and 17.5% HER2) compared to pure MPCs. A comparison between the distinct morphological components of mixed MPCs in a pairwise fashion revealed that both components harbour strikingly similar genomic profiles. When compared to grade‐ and ER‐matched IDC‐NSTs, mixed MPCs significantly more frequently harboured amplification of multiple regions on 8q (adjusted Fisher's p value < 0.05). Furthermore, mixed MPCs displayed higher proliferative rates than grade‐ and ER‐matched IDC‐NSTs. Our results suggest that micropapillary differentiation in breast cancer may identify a subgroup of more aggressive ER‐positive breast carcinomas, even in those featuring a mixed histology, and that mixed MPCs are more closely related to pure MPCs than to IDC‐NSTs. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

p53 mutation in breast cancer. Correlation with cell kinetics and cell of origin

AIM: Several studies have investigated the expression of the cytokeratins (CKs), vimentin, the epithelial growth factor receptor (EGFR), the oestrogen receptor (ER), and the progesterone receptor (PgR), in breast cancer, but no study has directly compared p53 mutations with these phenotypic and differentiation markers in the same case. The present study was designed to provide some of this information. METHODS: The expression of the p53 and bcl-2 proteins was evaluated by immunohistochemistry in relation to phenotypic characteristics and cellular kinetic parameters (mitotic index and apoptotic index) in 37 cases of ductal carcinoma in situ (DCIS) and 27 cases of infiltrating ductal carcinoma (IDC) of the breast. In addition, p53 gene mutation was examined by polymerase chain reaction single strand conformation polymorphism analysis (SSCP). RESULTS: Thirteen cases (eight DCIS and five IDC) showed expression of CK8, CK14, CK18, vimentin, and EGFR, consistent with a stem cell phenotype, whereas 44 cases (27 DCIS and 17 IDC) showed expression of CK8 and CK1, weak or negative expression of CK18, but were negative for vimentin and EGFR, consistent with a luminal cell phenotype. DCIS and IDC cases with a stem cell phenotype were ER/PgR negative and intermediately or poorly differentiated. In contrast, the cases with luminal cell phenotype were ER/PgR positive and well or intermediately differentiated. In addition, intermediately or poorly differentiated cases with a stem cell phenotype showed higher proliferative activity (per cent of MIB-l positive cells) than did intermediately or well differentiated cases with a luminal cell phenotype. Both DCIS and IDC cases with a stem cell phenotype were p53 positive and bcl-2 negative by immunohistochemistry. In IDC, p53 expression was associated with a reduction of both mitotic index and apoptotic index compared with DCIS. Most of the tumours showing a more differentiated phenotype (luminal) were p53 negative and bcl-2 positive. In these cases, cell kinetic parameters increased from DCIS to IDC. These data suggest the existence of subsets of DCIS and IDC that, because of their phenotypic characteristics, could be derived from subpopulations of normal breast cells having different control mechanisms of cell proliferation and neoplastic progression. CONCLUSIONS: These results are compatible with the hypothesis that the phenotype of the cell of origin constrains both tumour phenotype and the choice of genetic events; however, the occurrence of p53 mutants by chance during neoplastic transformation cannot be excluded.     

Ductal adenoma of the breast: Immunohistochemistry of two cases

The author reports herein two cases of ductal adenoma of the breast with an emphasis on immunohistochemistry. Both cases (patient 1, 58‐year‐old woman; patient 2, 78‐year‐old woman) were clinically suspected as carcinoma, and core biopsies were ‘indeterminate’ or ‘suspicious for malignancy’. Excisional biopsy and wide excision were performed. Histologically, both cases were ductal adenomas composed of ductal epithelial cells and myoepithelial cells. Patient 1 had extensive apocrine metaplasia. Immunohistochemically, myoepithelial cells were noted in both cases; cytokeratin (CK) 14 and p63 were the most reliable myoepithelial markers, followed by CD10, α‐smooth muscle actin and S100 protein. CK profile was as follows: positive expression of CK5/6, CK18, CK19, and high‐molecular‐weight CK, and negative expression of CK20. This CK profile was the same as that of non‐tumorous ducts, suggesting that the CK profile does not alter in tumorigenesis. The tumor cells expressed p53 protein ( case 1 , positive cell percentage 5%; case 2 , 7%), c‐erbB2 (HER2/neu, 76%, 64%), CEA (5%, 0%), estrogen receptor (33%, 84%), but were negative for progesterone receptor. Ki‐67 labeling was 5% and 3%, respectively. MUC apomucin expression was as follows: MUC1, 92%, 100%; MUC2, 0%, 0%; MUC5AC, 0%, 0%; and MUC6, 5%, 0%. Non‐tumorous ducts expressed MUC1, but were negative for MUC2, MUC5AC and MUC6.     

A subset of breast cancer predisposes to brain metastasis

This study evaluated the expression of biological markers of breast cancers with brain metastases. Eighteen paired tumors were assessed, with 42 non-brain-metastasizing breast cancers that were stained with ER, PR, HER2, CK5/6, p63, and Ki67, and were also classified into intrinsic subtypes. The expression patterns between the breast tumors with brain metastases were compared to the brain metastases and the controls. Breast cancers with brain metastases were of higher grade and showed higher incidence of lymph node metastases at initial diagnosis and higher EGFR, p63, and Ki67 expression. In the group of breast cancers with brain metastases, the brain metastases showed higher HER2, CK5/6, and Ki67 expression compared to the breast primaries. There was also a higher incidence of basal subtype and a lower incidence of luminal subtype. When tumors metastasized, changes in hormonal receptor (22%) and HER2 (6%) status were observed. We concluded that breast cancers with higher grade, lymph node involvement at diagnosis, high EGFR, p63, and Ki67 expression, and of basal subtype were at higher risk for brain metastases, and that both hormonal receptors and HER2 status may change in brain metastases.     

The expression of cytokeratin 5/6 in invasive lobular carcinoma of the breast: evidence of a basal-like subset?

Analysis of gene expression profiling data on breast cancers has revealed "molecular subclasses" that may have prognostic significance. The "basal-like" breast cancers, one of these molecular subclasses, have been associated with a significantly worse overall and disease-free survival as compared with most of the other subclasses. Previous studies on basal-like cancers have been performed predominantly on the ductal histotype. This study was designed to evaluate the significance of the expression of cytokeratin (CK) 5/6, a commonly used surrogate marker for the basal-like phenotype, in invasive lobular carcinomas (ILCs). The immunohistochemical expression of CK5/6, estrogen receptor (ER), progesterone receptor (PR), HER2/neu, and E-cadherin was determined in a group of 82 consecutive archived ILCs diagnosed in 82 women (age range, 29-73 years; mean, 51.9 years). All cases were E-cadherin negative. CK5/6 was positive in 14 (17%) of 82 cases and was entirely negative in the remaining 68 cases (83%). In 8 of the 14 CK5/6[+] cases, staining was diffuse and intense. In the remaining 6 cases, staining was patchy (>1 low-power field between positive areas) but still of high intensity. CK5/6[+] cases were significantly more likely than CK5/6[-] cases to be ER[-] (43% versus 0%, respectively, P < .0001). CK5/6[+] cases were also significantly more frequently of modified Scarff-Bloom-Richardson histologic grade 3, as 7 (50%) of the 14 CK5/6[+] cases were of histologic grade 3, as compared with only 6 (8.8%) of 68 of the CK5/6[-] cases (P = .0009). Notably, the average mitotic index in the CK5/6[+] group was 11/10 high-power fields, as compared with 7/10 high-power fields in the CK5/6[-] group (P = .07). Overall, there were no distinct morphological differences between the 2 groups, and both displayed the well-characterized architectural and cytologic features of ILCs. CK5/6[+] and CK5/6[-] cases did not significantly differ with respect to patient age, frequency of PR expression, tumor size, rate of axillary node involvement, or HER2/neu overexpression. In summary, the present study demonstrated that 17% of ILCs express CK5/6, and that CK5/6[+] cases are more likely to be ER[-] and have a high modified Scarff-Bloom-Richardson histologic grade. Because these findings are a characteristic of ductal basal-like breast cancers, our results suggest that there is a basal-like subset for ILCs with potentially distinct clinicopathologic characteristics. Future studies are required to define the prognostic significance of CK5/6 expression in ILCs.