Microglandular adenosis associated with triple‐negative breast cancer is a neoplastic lesion of triple‐negative phenotype harbouring TP53 somatic mutations

Microglandular adenosis (MGA) is a rare proliferative lesion of the breast composed of small glands lacking myoepithelial cells and lined by S100‐positive, oestrogen receptor (ER)‐negative, progesterone receptor (PR)‐negative, and HER2‐negative epithelial cells. There is evidence to suggest that MGA may constitute a non‐obligate precursor of triple‐negative breast cancer (TNBC). We sought to define the genomic landscape of pure MGA and of MGA, atypical MGA (AMGA) and associated TNBCs, and to determine whether synchronous MGA, AMGA, and TNBCs would be clonally related. Two pure MGAs and eight cases of MGA and/or AMGA associated with in situ or invasive TNBC were collected, microdissected, and subjected to massively parallel sequencing targeting all coding regions of 236 genes recurrently mutated in breast cancer or related to DNA repair. Pure MGAs lacked clonal non‐synonymous somatic mutations and displayed limited copy number alterations (CNAs); conversely, all MGAs (n = 7) and AMGAs (n = 3) associated with TNBC harboured at least one somatic non‐synonymous mutation (range 3–14 and 1–10, respectively). In all cases where TNBCs were analyzed, identical TP53 mutations and similar patterns of gene CNAs were found in the MGA and/or AMGA and in the associated TNBC. In the MGA/AMGA associated with TNBC lacking TP53 mutations, somatic mutations affecting PI3K pathway‐related genes (eg PTEN, PIK3CA, and INPP4B) and tyrosine kinase receptor signalling‐related genes (eg ERBB3 and FGFR2) were identified. At diagnosis, MGAs associated with TNBC were found to display subclonal populations, and clonal shifts in the progression from MGA to AMGA and/or to TNBC were observed. Our results demonstrate the heterogeneity of MGAs, and that MGAs associated with TNBC, but not necessarily pure MGAs, are genetically advanced, clonal, and neoplastic lesions harbouring recurrent mutations in TP53 and/or other cancer genes, supporting the notion that a subset of MGAs and AMGAs may constitute non‐obligate precursors of TNBCs. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Microglandular adenosis or microglandular adenoma? A molecular genetic analysis of a case associated with atypia and invasive carcinoma

Aims: Microglandular adenosis (MGA) is a rare breast lesion, which has long been considered to be hyperplastic. However, atypical forms of MGA (AMGA) and invasive carcinomas arising in the background of MGA are recorded. Recent studies have suggested that MGA may be a non‐obligate precursor of invasive carcinomas that are negative for hormone receptors and lack HER‐2 overexpression (triple‐negative phenotype). The aim of this study was to determine whether MGA is clonal and whether it harbours chromosomal aberrations similar to those found in matched invasive ductal carcinoma of no special type (IDC‐NST). Methods and results: We report on a case comprising MGA, AMGA and a high‐grade IDC‐NST. The three components were separately microdissected and subjected to genetic analysis with high‐resolution microarray comparative genomic hybridisation. Identical genetic changes were detected in all components with subsequent acquisition of additional genetic aberrations in the invasive component, suggesting that MGA was the substrate for the development of the invasive carcinoma. Immunohistochemistry revealed concordant profiles across all components, characterized by triple‐negative phenotype and variable positivity for basal markers. Conclusions: Similar to adenomas, MGA is, at least in some cases, a clonal lesion and may be a non‐obligate precursor of a subgroup of high‐grade triple‐negative and basal‐like breast carcinomas.     

Young‐aged woman with invasive ductal carcinoma arising in atypical microglandular adenosis: A case report

Microglandular adenosis (MGA) and atypical microglandular adenosis (AMGA) are extremely rare and unique forms of adenosis of the breast. Both forms of adenosis are strongly associated with carcinoma arising in microglandular adenosis (MGACA) and are recognised as precursor lesions of invasive breast carcinoma. Here we provide a clinical report of a young Taiwanese woman who was diagnosed with MGACA and AMGA by means of echo‐guided core biopsy. The subsequent lumpectomy revealed a spectrum of lesions ranging from MGA and AMGA to ductal carcinoma in situ (DCIS) and invasive carcinoma. All of the above lesions have similar immunohistochemical results (expression of S‐100 protein, the absence of oestrogen receptors, progesterone receptors and Her2/neu, and the lack of p63 and the smooth muscle myosin‐heavy chain) with a rather different Ki‐67 labelling proliferation index. This report is of practical interest because the diagnosis of AMGA and MGACA had already been made via needle biopsy.     

A case of matrix-producing carcinoma of the breast with micoglandular adenosis and review of literature

Matrix-producing carcinoma (MPC) of the breast is an extremely rare variant of metaplastic breast carcinoma that contains a mixture of epithelial and mesenchymal elements. As overt carcinoma with direct transition to a cartilaginous and/or osseous stromal matrix cells, MPC is of no spindle cells between those two elements. This is the case of a 43 year-old female patient with MPC which coexisted with microglandular adenosis (MGA), atypical MGA (AMGA) and carcinoma in situ arising in MGA (MGACA in situ). MGA is a rare, infiltrative, benign lesion of the breast with an indolent clinical course. Histological evidence of carcinoma arising from MGA has previously been documented. MPC arising in MGA is an extremely rare subtype of breast carcinoma and has been seldom detailed described in the previous studies. This report highlights one such case with cytomorphological and histopathological correlation, along with a review of pertinent literature and differential diagnosis.     

The repertoire of somatic genetic alterations of acinic cell carcinomas of the breast: an exploratory,hypothesis‐generating study

Acinic cell carcinoma (ACC) of the breast is a rare form of triple‐negative (that is, oestrogen receptor‐negative, progesterone receptor‐negative, HER2‐negative) salivary gland‐type tumour displaying serous acinar differentiation. Despite its triple‐negative phenotype, breast ACCs are reported to have an indolent clinical behaviour. Here, we sought to define whether ACCs have a mutational repertoire distinct from that of other triple‐negative breast cancers (TNBCs). DNA was extracted from microdissected formalin‐fixed, paraffin‐embedded sections of tumour and normal tissue from two pure and six mixed breast ACCs. Each tumour component of the mixed cases was microdissected separately. Tumour and normal samples were subjected to targeted capture massively parallel sequencing targeting all exons of 254 genes, including genes most frequently mutated in breast cancer and related to DNA repair. Selected somatic mutations were validated by targeted amplicon resequencing and Sanger sequencing. Akin to other forms of TNBC, the most frequently mutated gene found in breast ACCs was TP53 (one pure and six mixed cases). Additional somatic mutations affecting breast cancer‐related genes found in ACCs included PIK3CA, MTOR, CTNNB1, BRCA1, ERBB4, ERBB3, INPP4B, and FGFR2. Copy number alteration analysis revealed complex patterns of gains and losses similar to those of common forms of TNBCs. Of the mixed cases analysed, identical somatic mutations were found in the acinic and the high‐grade non‐acinic components in two out of four cases analysed, providing evidence of their clonal relatedness. In conclusion, breast ACCs display the hallmark somatic genetic alterations found in high‐grade forms of TNBC, including complex patterns of gene copy number alterations and recurrent TP53 mutations. Furthermore, we provide circumstantial genetic evidence to suggest that ACCs may constitute the substrate for the development of more aggressive forms of triple‐negative disease. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Breast cancer precursors revisited: molecular features and progression pathways

Lopez‐Garcia M A, Geyer F C, Lacroix‐Triki M, Marchió C & Reis‐Filho J S
(2010) Histopathology 57, 171–192
Breast cancer precursors revisited: molecular features and progression pathways Increasingly more coherent data on the molecular characteristics of benign breast lesions and breast cancer precursors have led to the delineation of new multistep pathways of breast cancer progression through genotypic–phenotypic correlations. It has become apparent that oestrogen receptor (ER)‐positive and ‐negative breast lesions are fundamentally distinct diseases. Within the ER‐positive group, histological grade is strongly associated with the number and complexity of genetic abnormalities in breast cancer cells. Genomic analyses of high‐grade ER‐positive breast cancers have revealed that a substantial proportion of these tumours harbour the characteristic genetic aberrations found in low‐grade ER‐positive disease, suggesting that at least a subgroup of high‐grade ER‐positive breast cancers may originate from low‐grade lesions. The ER‐negative group is more complex and heterogeneous, comprising distinct molecular entities, including basal‐like, HER2 and molecular apocrine lesions. Importantly, the type and pattern of genetic aberrations found in ER‐negative cancers differ from those of ER‐positive disease. Here, we review the available molecular data on breast cancer risk indicator and precursor lesions, the putative mechanisms of progression from in situ to invasive disease, and propose a revised model of breast cancer evolution based on the molecular characteristics of distinct subtypes of in situ and invasive breast cancers.     

Ductal epithelial proliferations of the breast: a biological continuum? Comparative genomic hybridization and high‐molecular‐weight cytokeratin expression patterns

According to current concepts, benign proliferative breast disease (BPBD) is a direct precursor of breast cancer, in a spectrum ranging from ductal hyperplasia to overtly invasive carcinoma. In this study, comparative genomic hybridization (CGH) was used to screen ductal hyperplasia and other BPBD lesions and ductal carcinoma in situ (DCIS) for common genomic abnormalities, to test the relationship between these hyperplastic and neoplastic lesions. Immunohistochemistry for cytokeratin 5/6 was used as a diagnostic adjunct to distinguish ductal hyperplasia from DCIS. A total of 42 cases of BPBD comprising ductal hyperplasia of the usual type (n=14), papilloma (n=22), tubular adenoma (n=3), and adenosis (n=3), as well as 52 cases of DCIS, were studied. All cases of BPBD consistently displayed the presence of a subpopulation of cytokeratin 5/6-expressing basal-type cells within the proliferative lesion, whereas all of the non-high-grade and most of the high-grade DCIS lesions lacked cytokeratin 5/6-positive cells. Whereas gross genomic alterations, as determined by CGH, were undetectable in BPBD, distinct genetic changes characterized all cases of DCIS, with one exception. These results confirm the usefulness of cytokeratin 5/6 immunohistology in the diagnosis of BPBD and neoplastic breast lesions and support the view that BPBD and DCIS are not closely related entities and that BPBD is not an obligate direct precursor of DCIS.     

Prevalence of BRCA1/2 large genomic rearrangements in Chinese women with sporadic triple‐negative or familial breast cancer

The prevalence of BRCA1/2 large genomic rearrangements (LGRs) and their underlying mechanisms have not been fully evaluated in Chinese women with breast cancer. In this study, we determined the prevalence of BRCA1/2 LGRs in 834 patients with familial breast cancer (FBC) and 660 patients with sporadic triple‐negative breast cancer (TNBC) who were negative for BRCA1/2 small‐range mutations using the multiplex ligation‐dependent probe amplification method. We found that 20 index patients (2.4%) in the FBC group carried a BRCA1 or BRCA2 LGR, and the frequencies of BRCA1 and BRCA2 LGRs were 1.6% and 0.8%, respectively. Seven index patients (1.1%) carried a BRCA1 LGR in 660 sporadic TNBC patients, whereas no BRCA2 LGRs were found in these patients. Among the BRCA1/2 LGRs, 48.1% (13/27) were novel, and the breakpoints of the majority of the LGRs were identified. ΨBRCA1‐mediated homologous recombination (HR) and Alu‐mediated HR/non‐homologous end‐joining (NHEJ) accounted for 40% and 30% of the BRCA1 LGRs, respectively. Alu‐mediated HR accounted for 71.4% of the BRCA2 LGRs, and the remaining one‐third was generated through Long interspersed nuclear elements (LINE)‐mediated NHEJ. Our findings suggest that both FBC patients and sporadic TNBC patients should be tested for BRCA1/2 LGRs.     

Invasion in breast lesions: the role of the epithelial–stroma barrier

Despite the significant biological, behavioural and management differences between ductal carcinoma in situ (DCIS) and invasive carcinoma of the breast, they share many morphological and molecular similarities. Differentiation of these two different lesions in breast pathological diagnosis is based typically on the presence of an intact barrier between the malignant epithelial cells and stroma; namely, the myoepithelial cell (MEC) layer and surrounding basement membrane (BM). Despite being robust diagnostic criteria, the identification of MECs and BM to differentiate in‐situ from invasive carcinoma is not always straightforward. The MEC layer around DCIS may be interrupted and/or show an altered immunoprofile. MECs may be absent in some benign locally infiltrative lesions such as microglandular adenosis and infiltrating epitheliosis, and occasionally in non‐infiltrative conditions such as apocrine lesions, and in these contexts this does not denote malignancy or invasive disease with metastatic potential. MECs may also be absent around some malignant lesions such as some forms of papillary carcinoma, yet these behave in an indolent fashion akin to some DCIS. In Paget's disease, malignant mammary epithelial cells extend anteriorly from the ducts to infiltrate the epidermis of the nipple but do not typically infiltrate through the BM into the dermis. Conversely, BM‐like material can be seen around invasive carcinoma cells and around metastatic tumour cell deposits. Here, we review the role of MECs and BM in breast pathology and highlight potential clinical implications. We advise caution in interpretation of MEC features in breast pathology and mindfulness of the substantive evidence base in the literature associated with behaviour and clinical outcome of lesions classified as benign on conventional morphological examination before changing classification to an invasive lesion on the sole basis of MEC characteristics.     

Carcinoma Arising in Microglandular Adenosis: An Immunohistochemical Analysis of 20 Intraepithelial and Invasive Neoplasms

Microglandular adenosis (MGA) of the breast is an uncommon, benign lesion that may mimic invasive carcinoma and has recently been recognized as having significant premalignant potential. When carcinomas arise in MGA, there is often a transition from ordinary MGA to atypical MGA (AMGA) to carcinoma. Nineteen cases of carcinoma arising in MGA are reported: 7 invasive carcinomas, 7 intraductal carcinomas (DCIS), and 5 with both invasive and intraductal carcinoma. A single case of AMGA without carcinoma is also reported. The 20 patients ranged in age from 36 to 81 years (mean 52). The most common clinical presentation was either a palpable mass (13 patients) or a mammographic abnormality (4 patients). All 20 cases contained AMGA, and in some cases AMGA was the predominant lesion. In 18 of the 19 cases with carcinoma, there was a clear transition from AMGA to the carcinoma. Twelve cases contained ordinary MGA, but in only 2 cases was MGA a prominent component of the lesion. In contrast to ordinary MGA, the glands of AMGA were more irregularly shaped, closely packed, and cytologically atypical and tended to lack secretions. A solid, occlusive proliferation of cells in the tubules was seen in 10 cases. All 12 examples of in situ carcinoma were either grade 2 or 3 and typically showed a solid proliferation of severely atypical cells within the glands; a cribrifrom pattern was also present in 1 case. The invasive carcinomas were morphologically diverse and included 2 with a basaloid morphology and 2 metaplastic carcinomas. Various immunostains were performed, and each lesion (AMGA, in situ, and invasive carcinoma) was separately assessed for immunoreactivity. As expected, S-100 was positive in the vast majority of AMGA and in situ carcinomas and in all 12 invasive carcinomas. S-100beta was also positive in the majority of cases although the staining was weaker. Laminin and type IV collagen highlighted the basement membrane around the AMGA and in situ carcinoma and are useful stains in difficult cases. Except for a single case, ER and PR were negative in all lesions. Cytokeratin 7 (CK 7) was positive, while cytokeratin 20 (CK 20) was negative in all cases. Immunostains for CK903 showed no reactivity in any of the invasive carcinomas, in situ carcinomas, or atypical MGA but was focally present in the associated MGA in 2 of the 8 cases studied. Immunostains for MIB-1 and p53 were semiquantitatively assessed and both were positive in AMGA but tended to show a more intense staining in the carcinomas. Five cases were also studied for immunoexpression of alpha-1 antitrypsin (AAT), alpha-1 antichymotrypsin (ACTP), lysozyme, and salivary gland amylase. All 5 invasive carcinomas were positive for ACTP, though the staining was very focal in about 10% of the cells in a basaloid carcinoma. The in situ carcinoma as well as the AMGA in 4 of the 5 cases were positive for ACTP. Three of the 5 invasive carcinomas were positive for AAT in 10% to 40% of the cells. The most intense positivity for AAT and ACTP was in cells with coarsely granular apocrine appearance evident in 2 of the 5 cases. Four of the 5 invasive carcinomas were positive for lysozyme in 10% to 50% of the cancer cells; the in situ carcinoma and the associated AMGA showed similar immunoreaction in each case. None of the 5 cases showed convincing positivity for salivary gland amylase. The MGA in all 5 cases was negative for AAT and ACTP; the MGA in 1 of the 5 cases was positive for lysozyme. This study confirms the potential of MGA to develop into an invasive carcinoma, more clearly defines the features of AMGA, highlights the importance of AMGA in the evolution of carcinoma from MGA, and expands our knowledge of the immunophenotype of AMGA and the carcinomas arising from it. The diagnostic criteria briefly noted previously for diagnosis of AMGA and carcinoma arising in MGA are expanded and formally proposed. Int J Surg Pathol 8(4):303-315, 2000     

Expression of autophagy‐related markers beclin‐1, light chain 3A,light chain 3B and p62 according to the molecular subtype of breast cancer

Aims: To investigate the relationship between the expression of autophagy‐related proteins, including beclin‐1, light chain (LC) 3A, LC3B, and p62, and prognosis in invasive breast cancer. Methods and results: We constructed tissue microarrays from the breast cancer cells of 489 patients, and classified molecular subtypes using surrogate immunohistochemical stains. The tumoral expression levels of LC3A and LC3B were highest in triple‐negative breast cancer (TNBC) (P < 0.001), whereas these types of tumour had the lowest expression levels of these markers in the stroma (P = 0.005 and P < 0.001, respectively). Cytoplasmic beclin‐1 expression was highest in TNBC, but nuclear expression was lowest (P < 0.001). p62 cytoplasmic and nuclear expression were highest in HER2‐type tumours (P = 0.001 and P < 0.001, respectively). Tumoral LC3A and LC3B expression were associated with high histological grade (P < 0.001, and P < 0.028, respectively), but nuclear p62 expression was associated with lower histological grade (P = 0.004). Conclusions: Autophagy‐related markers are differentially expressed according to the molecular subtype of breast cancer. In particular, expression of LC3A, LC3B and beclin‐1 was highest in TNBC tumour cells, whereas that of LC3A and LC3B in the tumour stroma was lowest in TNBC.     

Distribution of aldehyde dehydrogenase 1-positive stem cells in benign mammary tissue from women with and without breast cancer

Isfoss B L, Holmqvist B, Alm P & Olsson H
(2012) Histopathology  60, 617–633
Distribution of aldehyde dehydrogenase 1‐positive stem cells in benign mammary tissue from women with and without breast cancer Aims: Aldehyde dehydrogenase 1 (ALDH1) in female breast tissue has been linked to stem cells, but little is known about the benign cellular organization in situ. We investigated the distribution of ALDH1‐immunoreactive (ALDH1+) cells in histomorphologically benign breast tissue from 28 women with or without breast cancer. Methods and results: ALDH1+ cells were detected in benign tissue of women aged 20–72 years, located most commonly at the luminal and intermediate ductular levels and in the stroma. ALDH1+ cell populations and Ki67+ cell populations were present in separate ductules, both cell types rarely showing epithelial differentiation. ALDH1+ cells were non‐reactive to Ki67 and oestrogen receptor. Stromal round/oval ALDH1+ non‐leukocyte cells in both age groups expressed contractile protein. There was a lower concentration of luminal and intermediate ductular ALDH1+ cells in postmenopausal women than in premenopausal women, and in cancer patients than in non‐cancer patients, and a higher concentration in women receiving exogenous hormones. Conclusions: This study provides further evidence for the stem cell character of ALDH1+ cells, here in benign breast tissue of cancer and non‐cancer patients throughout non‐lactating adult life, and contributes evidence of benign stromal ALDH1+ cells. The distribution of ductular ALDH1+ stem cells appears to be influenced by hormonal status.     

Divergent behaviour of oxidative stress markers 8-hydroxydeoxyguanosine (8-OHdG) and 4-hydroxy-2-nonenal (HNE) in breast carcinogenesis

Karihtala P, Kauppila S, Puistola U & Jukkola‐Vuorinen A
(2011) Histopathology 58, 854–862
Divergent behaviour of oxidative stress markers 8‐hydroxydeoxyguanosine (8‐OHdG) and 4‐hydroxy‐2‐nonenal (HNE) in breast carcinogenesis Aims: To clarify the role of oxidative stress during breast carcinogenesis by studying the expression of 8‐hydroxydeoxyguanosine (8‐OHdG) (a marker of oxidative DNA damage) and 4‐hydroxy‐2‐nonenal (HNE) (a marker of lipid peroxidation) during the different phases of breast carcinogenesis. Methods and results: The study material consisted of a total of 219 patients: 31 with usual ductal hyperplasia (UDH), 25 with atypical ductal hyperplasia (ADH), 30 with ductal carcinoma in situ (DCIS) and 133 with invasive carcinoma. The expression of 8‐OHdG and HNE were evaluated immunohistochemically. Both 8‐OHdG (77.4%) and HNE (45.8%) expression was already seen in UDH lesions. Interestingly, the trend of these two immunostainings during breast carcinogenesis was diverse. 8‐OHdG expression diminished significantly in invasive breast carcinomas compared to non‐invasive lesions (P < 0.005 when set against non‐invasive cohorts). Also within the same lesions, 8‐OHdG expression was the most intensive in benign cells. Conversely, HNE immunostaining was strongest in invasive breast carcinomas (UDH versus invasive cohort, P = 0.015). Conclusions: 4‐hydroxy‐2‐nonenal as a marker of lipid peroxidation increases during breast carcinogenesis, reflecting the role of oxidative stress in the pathogenesis of breast cancer. However, 8‐OHdG shows diminished levels in carcinomas, possibly resulting from the induction of DNA repair in these invasive lesions.     

Classification of breast lesions pre‐contrast injection using water resonance lineshape analysis

Inhomogeneously broadened, non‐Lorentzian water resonances have been observed in small image voxels of breast tissue. The non‐Lorentzian components of the water resonance are probably produced by bulk magnetic susceptibility shifts caused by dense, deoxygenated tumor blood vessels (the ‘blood oxygenation level‐dependent’ effect), but can also be produced by other characteristics of local anatomy and physiology, including calcifications and interfaces between different types of tissue. Here, we tested the hypothesis that the detection of non‐Lorentzian components of the water resonance with high spectral and spatial resolution (HiSS) MRI allows the classification of breast lesions without the need to inject contrast agent. Eighteen malignant lesions and nine benign lesions were imaged with HiSS MRI at 1.5 T. A new algorithm was developed to detect non‐Lorentzian (or off‐peak) components of the water resonance. After a Lorentzian fit had been subtracted from the data, the largest peak in the residual spectrum in each voxel was identified as the major off‐peak component of the water resonance. The difference in frequency between these off‐peak components and the main water peaks, and their amplitudes, were measured in malignant lesions, benign lesions and breast fibroglandular tissue. Off‐peak component frequencies were significantly different between malignant and benign lesions (p < 0.001). Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of HiSS off‐peak component analysis compared with dynamic contrast‐enhanced (DCE) MRI parameters. The areas under the ROC curves for the ‘DCE rapid uptake fraction’, ‘DCE washout fraction’, ‘off‐peak component amplitude’ and ‘off‐peak component frequency’ were 0.75, 0.83, 0.50 and 0.86, respectively. These results suggest that water resonance lineshape analysis performs well in the classification of breast lesions without contrast injection and could improve the diagnostic accuracy of clinical breast MR examinations. In addition, this approach may provide an alternative to DCE MRI in women who are at risk for adverse reactions to contrast media. Copyright © 2012 John Wiley & Sons, Ltd.     

Epigenetic silencing in non‐neoplastic epithelia identifies E‐cadherin (CDH1) as a target for chemoprevention of lobular neoplasia

Invasive lobular carcinoma (ILC) of the breast is believed to develop from in situ lesions, atypical lobular hyperplasia (ALH), and lobular carcinoma in situ (LCIS). Down‐regulation of the cell–cell adhesion protein E‐cadherin is a defining feature of lobular breast cancer (LBC) and already occurs in ALH and LCIS. Apart from mutational mechanisms, epigenetic silencing of the E‐cadherin gene (CDH1) is thought to be involved in E‐cadherin down‐regulation and has been observed at a high frequency in ILC. Whether CDH1 promoter methylation is already present in in situ lesions and thus contributes to the initiation of LBC is not established. We thus examined microdissected archived tissue from 20 LBCs by methylation‐specific PCR to determine the CDH1 methylation status of lobular lesions. Nineteen of the 20 LBCs had a hypermethylated CDH1 promoter, including 13/14 ILCs and 13/13 ALHs or LCIS. Bisulphite sequencing indicated that methylation was complete within the investigated promoter fragment. Intriguingly, CDH1 methylation was likewise present in 8/8 adjacent non‐neoplastic epithelia, but not in 6/6 mammary epithelia from healthy subjects. E‐cadherin protein and mRNA were down‐regulated in in situ lesions relative to adjacent epithelia. Together, these results indicate that CDH1 promoter methylation occurs in LBC prior to E‐cadherin down‐regulation and neoplastic formation. We thus propose that epigenetic silencing represents the first of the two hits required to silence both CDH1 alleles for LBC to develop. Because promoter methylation is in principle reversible, our findings suggest that chemoprevention of LBC by epigenetic drugs should be feasible. Furthermore, the presence of CDH1 methylation in pre‐neoplastic epithelia suggests the existence of mammary regions with increased disease susceptibility, providing an explanation for the often multifocal presentation of LBC. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Concurrent DNA Copy‐Number Alterations and Mutations in Genes Related to Maintenance of Genome Stability in Uninvolved Mammary Glandular Tissue from Breast Cancer Patients

Somatic mosaicism for DNA copy‐number alterations (SMC‐CNAs) is defined as gain or loss of chromosomal segments in somatic cells within a single organism. As cells harboring SMC‐CNAs can undergo clonal expansion, it has been proposed that SMC‐CNAs may contribute to the predisposition of these cells to genetic disease including cancer. Herein, the gross genomic alterations (>500 kbp) were characterized in uninvolved mammary glandular tissue from 59 breast cancer patients and matched samples of primary tumors and lymph node metastases. Array‐based comparative genomic hybridization showed 10% (6/59) of patients harbored one to 359 large SMC‐CNAs (mean: 1,328 kbp; median: 961 kbp) in a substantial portion of glandular tissue cells, distal from the primary tumor site. SMC‐CNAs were partially recurrent in tumors, albeit with considerable contribution of stochastic SMC‐CNAs indicating genomic destabilization. Targeted resequencing of 301 known predisposition and somatic driver loci revealed mutations and rare variants in genes related to maintenance of genomic integrity: BRCA1 (p.Gln1756Profs*74, p.Arg504Cys), BRCA2 (p.Asn3124Ile), NCOR1 (p.Pro1570Glnfs*45), PALB2 (p.Ser500Pro), and TP53 (p.Arg306*). Co‐occurrence of gross SMC‐CNAs along with point mutations or rare variants in genes responsible for safeguarding genomic integrity highlights the temporal and spatial neoplastic potential of uninvolved glandular tissue in breast cancer patients.     

Recommendations for excision following core needle biopsy of the breast: a contemporary evaluation of the literature

Pathologists frequently encounter non‐malignant histological findings in percutaneous core needle biopsies (CNBs). Standards for the management of patients with lesions such as atypical ductal hyperplasia, atypical lobular hyperplasia, and lobular carcinoma in situ, as well as other benign lesions, are not well defined, and recommendations for surgical biopsy or continued clinical and radiological follow‐up are inconsistent. The frequency with which these lesions are ‘upgraded’ to carcinoma in excision specimens is widely variable in the literature. Many CNB studies lack careful radiological–pathological correlation, clear criteria for excision, and clinical follow‐up for patients on whom excision was not performed. This review of the recent literature emphasizes studies with radiological–pathological correlation, with the goal of developing a contemporary, evidence‐based approach to the management of non‐malignant lesions of the breast diagnosed on CNB. The data supporting an emerging consensus on which lesions may not require excision are highlighted. The management of non‐malignant lesions diagnosed on magnetic resonance imaging‐guided CNB is also discussed.