Breast lesions of uncertain malignant nature and limited metastatic potential: proposals to improve their recognition and clinical management.

Breast lesions comprise a family of heterogeneous entities with variable patterns of presentation, morphology and clinical behaviour. The majority of breast lesions are classified traditionally into benign and malignant conditions and their behaviour can, in the vast majority of cases, be predicted with a reasonable degree of accuracy. However, there remain lesions which show borderline features and lie in a grey zone between benign and malignant, as their behaviour cannot be predicted reliably. Defined pathological categorization of such lesions is challenging, and for some entities is recognized to be subjective and include a range of diagnoses, and forms of terminology, which may trigger over- or undertreatment. The rarity of these lesions makes the acquisition of clinical evidence problematic and limits the development of a sufficient evidence base to support informed decision-making by clinicians and patients. Emerging molecular evidence is providing a greater understanding of the biology of these lesions, but this may or may not be reflected in their clinical behaviour. Herein we discuss some breast lesions that are associated with uncertainty regarding classification and behaviour, and hence management. These include biologically invasive malignant lesions associated with uncertain metastatic potential, such as low-grade adenosquamous carcinoma, low-grade fibromatosis-like spindle cell carcinoma and encapsulated papillary carcinoma. Other lesions of uncertain malignant nature remain, such as mammary cylindroma, atypical microglandular adenosis, mammary pleomorphic adenoma and infiltrating epitheliosis. The concept of categories of (1) breast lesions of uncertain malignant nature and (2) breast lesions of limited metastatic potential are proposed with details of which histological entities could be included in each category, and their management implications are discussed.

Phyllodes tumours of the breast: a consensus review.

Phyllodes tumours constitute an uncommon but complex group of mammary fibroepithelial lesions. Accurate and reproducible grading of these tumours has long been challenging, owing to the need to assess multiple stratified histological parameters, which may be weighted differently by individual pathologists. Distinction of benign phyllodes tumours from cellular fibroadenomas is fraught with difficulty, due to overlapping microscopic features. Similarly, separation of the malignant phyllodes tumour from spindle cell metaplastic carcinoma and primary breast sarcoma can be problematic. Phyllodes tumours are treated by surgical excision. However, there is no consensus on the definition of an appropriate surgical margin to ensure completeness of excision and reduction of recurrence risk. Interpretive subjectivity, overlapping histological diagnostic criteria, suboptimal correlation between histological classification and clinical behaviour and the lack of robust molecular predictors of outcome make further investigation of the pathogenesis of these fascinating tumours a matter of active research. This review consolidates the current understanding of their pathobiology and clinical behaviour, and includes proposals for a rational approach to the classification and management of phyllodes tumours.

Genomic profiling of mitochondrion-rich breast carcinoma: chromosomal changes may be relevant for mitochondria accumulation and tumour biology.

Oncocytic carcinomas are composed of mitochondrion-rich cells. Though recognised by the WHO classification as a histological special type of breast cancer, their status as a discrete pathological entity remains a matter of contention. Given that oncocytic tumours of other anatomical sites display distinct clinico-pathological and molecular features, we sought to define the molecular genetic features of mitochondrion-rich breast tumours and to compare them with a series of histological grade- and oestrogen receptor status-matched invasive ductal carcinomas of no special type. Seventeen mitochondrion-rich breast carcinomas, including nine bona fide oncocytic carcinomas, were profiled with antibodies against oestrogen, progesterone and androgen receptors, HER2, Ki67, GCDFP-15, chromogranin, epithelial membrane antigen, cytokeratin 7, cytokeratin 14, CD68 and mitochondria antigen. These tumours were microdissected and DNA extracted from samples with >70% of tumour cells. Fourteen cases yielded DNA of sufficient quality/quantity and were subjected to high-resolution microarray comparative genomic hybridisation analysis. The genomic profiles were compared to those of 28 grade- and oestrogen receptor status-matched invasive ductal carcinomas of no special type. Oncocytic and other mitochondrion-rich tumours did not differ significantly between themselves. As a group, mitochondrion-rich carcinomas were immunophenotypically heterogenous. Recurrent copy number changes were similar to those described in unselected breast cancers. However, unsupervised and supervised analysis identified a subset of mitochondrion-rich cancers, which often displayed gains of 11q13.1-q13.2 and 19p13. Changes in the latter two chromosomal regions have been shown to be associated with oncocytic tumours of the kidney and thyroid, respectively, and host several nuclear genes with specific mitochondrial function. Our results indicate that in a way akin to oncocytic tumours of other anatomical sites, at least a subset of mitochondrion-rich breast carcinomas may be underpinned by a distinct pattern of chromosomal changes potentially relevant for mitochondria accumulation and constitute a discrete molecular entity.

Expression of p63 is the sole independent marker of aggressiveness in localised (stage I-II) Merkel cell carcinomas.

Merkel cell carcinoma of the skin is a malignant neuroendocrine tumour, whose prognostic criteria are a matter of dispute. Specifically, no predictor is presently available in stage I-II tumours. We collected clinical and follow-up data from 70 Merkel cell carcinomas of the skin. The same cases were studied for p63 expression by immunohistochemistry, by reverse-transcription PCR (RT-PCR) and TP63 gene status by FISH and for presence of Merkel cell polyomavirus by PCR. Stage emerged as a significant prognostic parameter (P=0.008). p63 expression, detected in 61% (43/70) of cases by immunohistochemistry, was associated with both decreased overall survival (P<0.0001) and disease-free survival (P<0.0001). Variable expression patterns of the different p63 isoforms were found only in cases immunoreactive for p63. In these latter lesions, at least one of the N-terminal p63 isoforms was detected and TAp63α was the most frequently expressed isoform. TP63 gene amplification was observed by FISH in only one case. Presence of Merkel cell polyomavirus DNA sequences was detected in 86% (60/70) of Merkel cell carcinomas and did not emerge as a significant prognostic parameter. Merkel cell carcinoma cases at low stage (stage I-II) represented over half (40/70 cases, 57%) of cases, and the clinical course was uneventful in 25 of 40 cases while 15 cases died of tumour (10/40 cases) within 34 months or were alive with disease (5/40 cases) within 20 months. Interestingly, a very strict correlation was found between evolution and p63 expression (P<0.0001). The present data indicate that p63 expression is associated with a worse prognosis in patients with Merkel cell carcinoma, and in localised tumours it represents the single independent predictor of clinical evolution.

Basal-like and triple-negative breast cancers: a critical review with an emphasis on the implications for pathologists and oncologists.

Breast cancer is a heterogeneous disease encompassing a variety of entities with distinct morphological features and clinical behaviors. Although morphology is often associated with the pattern of molecular aberrations in breast cancers, it is also clear that tumors of the same histological type show remarkably different clinical behavior. This is particularly true for 'basal-like cancer', which is an entity defined using gene expression analysis. The purpose of this article was to review the current state of knowledge of basal-like breast cancers, to discuss the relationship between basal-like and triple-negative breast cancers, and to clarify practical implications of these diagnoses for pathologists and oncologists.

Breast cancer prognostic classification in the molecular era: the role of histological grade.

Breast cancer is a heterogeneous disease with varied morphological appearances, molecular features, behavior, and response to therapy. Current routine clinical management of breast cancer relies on the availability of robust clinical and pathological prognostic and predictive factors to support clinical and patient decision making in which potentially suitable treatment options are increasingly available. One of the best-established prognostic factors in breast cancer is histological grade, which represents the morphological assessment of tumor biological characteristics and has been shown to be able to generate important information related to the clinical behavior of breast cancers. Genome-wide microarray-based expression profiling studies have unraveled several characteristics of breast cancer biology and have provided further evidence that the biological features captured by histological grade are important in determining tumor behavior. Also, expression profiling studies have generated clinically useful data that have significantly improved our understanding of the biology of breast cancer, and these studies are undergoing evaluation as improved prognostic and predictive tools in clinical practice. Clinical acceptance of these molecular assays will require them to be more than expensive surrogates of established traditional factors such as histological grade. It is essential that they provide additional prognostic or predictive information above and beyond that offered by current parameters. Here, we present an analysis of the validity of histological grade as a prognostic factor and a consensus view on the significance of histological grade and its role in breast cancer classification and staging systems in this era of emerging clinical use of molecular classifiers.

Classifications and prognosis of breast cancer: from morphology to molecular taxonomy.

In 2003, the WHO breast tumours classification was published. It was primarily histological, but in each chapter, a section of cytogenetic as well as molecular pathology was present. The various problems of terminology were solved introducing for each histological group a paragraph where most of the synonyms were included. When an agreement was not reached, a table was presented where the different terminologies were compared. This was mostly evident for the intraductal neoplastic proliferations and accordingly the traditional terminology of Ductal Carcinoma in Situ was taken in consideration, together with the "novel" terminology of Ductal Intraepithelial Neoplasia. Using microarrays, Sorlie et al. were able to classify breast cancer along six different categories of which basal-like was at an extreme representing the most undifferentiated tumours and luminal subtype A represented the majority of their cases which probably were the most differentiated. The advantages and disadvantages of the recent molecular classifications are discussed.

Epitheliosis, infiltrating epitheliosis, and radial scar.

The lesion termed "infiltrating epitheliosis" (IE) by Azzopardi is described using his original criteria. The differential diagnosis from radial scar (RS) is discussed. It appears that IE and RS are histologically and histogenetically different and are also associated with a different risk of carcinoma. IE can be associated with either in situ or invasive carcinoma, whereas RS being more like a process of involution is very seldom involved by a carcinoma. Therefore, whatever name is used among the several found in the literature, it should be made clear they are not interchangeable when reporting on lesions like IE and RS.

Rare (new) entities of the breast and medullary carcinoma.

Rare tumours are a heterogeneous group of conditions that encompass benign to malignant lesions both of stromal and epithelial origin. Here some of these tumours are described, in which the authors have most familiarity. An outline of medullary carcinoma is also presented.

The pre-lymphatic pathway, the rooths of the lymphatic system in breast tissue: a 3D study.

Three-dimensional (3D) visualisation of microscopic structures provides useful information about their configuration and the spatial (hence functional) relationship between different components in tissues. This paper describes 3D dynamic reconstructions of the pre-lymphatic labyrinth in two cases of "normal" breast core biopsies and one case of pseudoangiomatous stromal hyperplasia. Direct anastomoses between pre-lymphatic channels and true lymphatics of the breast were demonstrated. It is concluded that pre-lymphatics are a way of communication between breast epithelial/stromal structures and the main lymphatic system. The present findings suggest that the existence of pre-lymphatics has to be taken in consideration in the intramammary spread of malignant tumours.

Trisomy of chromosome 6 in Merkel cell carcinoma within lymph nodes.

Merkel cell carcinoma (MCC) of the skin is a neuroendocrine tumor with characteristic histological and immunohistochemical features. Among various cytogenetic changes, trisomy of chromosome 6 has been reported in 47% of cases using in situ hybridization. Primary tumors, morphologically and immunohistochemically identical to MCCs of the skin, have been described in other organs, including lymph nodes. Here, a cytogenetic study of four cases of MCC of lymph nodes is presented. Four cases of primary MCCs of lymph nodes and ten cases of cutaneous MCCs were studied for chromosome 6 using fluorescent in situ hybridization (FISH). All cases showed typical features of MCC both at hematoxylin and eosin (H&E) and immunohistochemistry. FISH showed trisomy 6 in two out of the four cases ofMCCs of lymph node as well as in 6 out 10 cases of MCCs of skin. Lymph nodal and cutaneous MCCs share same histological and immunohistochemical features, as well as same cytogenetic alteration for chromosome 6. It seems that there are more similarities than differences between cutaneous and lymph nodal MCCs. Whether lymph nodal MCCs are primary tumors or metastases from regressed skin lesions is still questionable, although several findings indicate a primary origin.

Gene expression profiling in glioblastoma and immunohistochemical evaluation of IGFBP-2 and CDC20.

Thirty-nine glial tumours (28 glioblastomas (GB) and 11 low-grade gliomas) were investigated with DNA microarrays to reveal a possible specific gene expression profile. Unsupervised classification through hierarchical cluster analysis identified two groups of tumours, the first composed of low-grade gliomas and the second mainly composed of GB. Nine genes were identified as most informative: seven were over-expressed in low-grade gliomas and under-expressed in GB; on the contrary, two genes, insulin-like growth factor binding protein 2 (IGFBP-2) and cell division cycle 20 homologue (CDC20), were over-expressed in GB and under-expressed in low-grade tumours. This same genetic profile was confirmed by reverse transcriptase polymerase chain reaction. Immunohistochemistry for IGFBP-2 was positive in 88.8% of the cases of GB and in only one low-grade glioma, whilst CDC20 immunostained 74.1% of the cases of GB and none low-grade glioma. This was confirmed in an additional series of cases studied with immunohistochemistry only. In conclusion, over-expression of mRNA levels of IGFBP-2 and CDC20 is highly related to GB, IGFBP-2 and CDC-20 gene and protein expressions are strongly correlated, and IGFBP-2 and CDC20 immunopositivity can be useful for the identification of GB in small biopsies.

Microglandular adenosis of the breast: a deceptive and still mysterious benign lesion.

Microglandular adenosis (MA) of the breast, a benign glandular proliferation, was originally described approximately 35 years ago. The lesion is constituted by small glands, all of the same size. Glands are lined by one layer of cuboidal epithelial cells encircled by basal lamina without any evidence of interposed myoepithelial elements. Cells are positive for low-weight keratins and S-100 protein and negative for estrogen receptor, progesterone receptor, and HER-2. Since then, in the years that followed, several malignant lesions all showing microglandular architecture have been regarded either as a precursor or as an equivalent manifestation of MA. The latter has been associated with a large number of malignancies that include ductal carcinoma in situ, lobular carcinoma in situ, ademyoepithelioma, high-grade basal-like carcinoma, adenoid cystic carcinoma, matrix-producing carcinoma, invasive duct carcinoma not otherwise specified, and spindle cell carcinoma, not to mention acinic cell carcinoma. None of the above tumors were identical to MA. Differences mainly rested not only on the specific structure of the small glands but also on the cytological composition and immunohistochemical features of different lesions. Here, a review of the features of MA together with the differential diagnosis with lesions showing microglandular structure is discussed. MA shows similarities to a lesion named microglandular hamartoma/adenosis of the nasal cavity. The relation of the 2 similar lesions is discussed.

Sentinel lymph node biopsy and non-sentinel node involvement in special type breast carcinomas with a good prognosis.

This study aimed at identifying factors related to sentinel lymph node (SLN) involvement in patients with tubular, cribriform, mucinous or papillary breast carcinoma and those related to non-SLN metastases if an SLN was positive. Multivariate analyses involved logistic and stepwise regressions. The SLNs harboured metastases in 85 of 572 cases, 78 of whom underwent axillary dissection; 19 presented non-SLN positive disease. Lack of lymphovascular invasion, a tumour size < or = 10 mm and a single SLN removed were the factors predicting an SLN metastasis rate <10%, and patients with these features could be candidates for no surgical axillary staging. A positive SLN proportion of < or = 50% and no lymphovascular invasion were associated with a <10% rate of non-SLN invasion; patients with a positive SLN and these features could be candidates for the omission of completion axillary dissection. The opposite presentation of these factors would mandate SLN biopsy and axillary dissection, respectively.

Squamous cell carcinoma in situ of the breast: a light microscopic and immunohistochemical study of a previously undescribed lesion.

Three cases of squamous carcinoma in situ of the breast, one with an invasive component are described in women aged 35, 51, and 59 years. Two cases were detected by screening mammography. In 1 case, the squamous ductal carcinoma in situ was extensive. All cases showed obvious squamous features on standard hematoxylin and eosin sections. The in situ component of the lesions and the squamous differentiation were supported by immunohistochemistry. In 2 cases, the neoplastic cells showed actin positivity indicating myoepithelial cell differentiation. One case showed trilineage differentiation into luminal, squamous, and myoepithelial cells. These cases illustrate a variant of duct carcinoma in situ that has not been described in the current literature and provide insights into the dual epithelial-myoepithelial differentiation of some breast neoplasms.

The impact of large sections on the study of in situ and invasive duct carcinoma of the breast.

Large histologic sections (LHSs) are increasingly used in the study of normal and neoplastic breast tissue. LHSs allow the direct visualization of a large part of the breast glandular tree. Accordingly, LHSs have shown that in situ and invasive lobular carcinoma is a multilobar (and hence multifocal) neoplastic lesion in more than 50% of the cases, and that poorly differentiated duct carcinoma in situ (DCIS grade 3) is frequently unifocal, whereas it is often multifocal when the in situ lesion is a well-differentiated type (DCIS grade 1). Forty-five mastectomies were studied with large sections. Mastectomies were performed when quadrantectomy did not guarantee radical excision of the tumor with adequate cosmesis because of the large size of the lesion or because the neoplastic lesion was located below the nipple. Excluded were cases of lobular neoplasia or invasive lobular carcinoma, because they were reported separately, and cases of mastectomies performed for sarcoma or recurrent phyllodes tumor. All cases had undergone a preoperative diagnostic procedure (fine needle aspiration), and the relative positive material was reviewed. All 45 cases showed in situ duct carcinoma and 37 showed evidence of invasive duct carcinoma. Forty-two cases of DCIS were multifocal, whereas only 4 invasive duct carcinoma were shown as multifocal. When DCIS lesions were subdivided into 3 grades, no statistical significance was seen among the 3 groups of DCIS in regard to multifocality. Nevertheless, DCIS grade 1 was a widespread condition involving more than one lobe and quadrant, whereas DCIS grades 2 and 3 appeared more localized. DCIS grade 1 was more similar to that previously observed in lobular in situ neoplasia/lobular in situ carcinoma. In 66.6% of the cases, DCIS foci were found within the invasive areas, indicating a more than fortuitous occurrence (2-sided P=.0357).

Sentinel lymph node biopsy in staging small (up to 15 mm) breast carcinomas. Results from a European multi-institutional study.

Sentinel lymph node (SLN) biopsy has become the preferred method for the nodal staging of early breast cancer, but controversy exists regarding its universal use and consequences in small tumors. 2929 cases of breast carcinomas not larger than 15 mm and staged with SLN biopsy with or without axillary dissection were collected from the authors' institutions. The pathology of the SLNs included multilevel hematoxylin and eosin (HE) staining. Cytokeratin immunohistochemistry (IHC) was commonly used for cases negative with HE staining. Variables influencing SLN involvement and non-SLN involvement were studied with logistic regression. Factors that influenced SLN involvement included tumor size, multifocality, grade and age. Small tumors up to 4 mm (including in situ and microinvasive carcinomas) seem to have SLN involvement in less than 10%. Non-SLN metastases were associated with tumor grade, the ratio of involved SLNs and SLN involvement type. Isolated tumor cells were not likely to be associated with further nodal load, whereas micrometastases had some subsets with low risk of non-SLN involvement and subsets with higher proportion of further nodal spread. In situ and microinvasive carcinomas have a very low risk of SLN involvement, therefore, these tumors might not need SLN biopsy for staging, and this may be the approach used for very small invasive carcinomas. If an SLN is involved, isolated tumor cells are rarely if ever associated with non-SLN metastases, and subsets of micrometastatic SLN involvement may be approached similarly. With macrometastases the risk of non-SLN involvement increases, and further axillary treatment should be generally indicated.

The morphological spectrum of salivary gland type tumours of the breast.

Salivary gland like tumours of the breast constitute a wide spectrum of entities each one showing peculiar features and clinical behaviour. They can be subdivided as follows: (1) tumours showing pure myoepithelial cell differentiation, such as pure benign and malignant myoepitheliomas; (2) tumours with mixed epithelial and myoepithelial cell differentiation, such as pleomorphic adenoma, adenomyoepithelioma and adenoid cystic carcinoma; and (3) tumours with pure epithelial cell differentiation, such as acinic cell carcinoma, oncocytic carcinoma, mucoepidermoid carcinoma and polymorphous adenocarcinoma. These tumours share similar features with the salivary gland counterparts, but different clinical behaviour. Most salivary gland type tumours of the breast are negative for oestrogen and progesterone receptor and lack HER2 gene amplification, therefore they are classified as 'triple negative' tumours. Nevertheless, some of the malignant entities (such as classical adenoid cystic carcinoma) exhibit good behaviour and do not need any treatment in addition to local control. The aim of the present paper is to review the morphological and prognostic features of salivary gland like tumours of the breast, in order to highlight the correct clinical management.

Solid Papillary Breast Carcinomas Resembling the Tall Cell Variant of Papillary Thyroid Neoplasms: A Unique Invasive Tumor With Indolent Behavior.

Thirteen cases of invasive solid papillary breast carcinomas resembling the tall cell variant of papillary thyroid neoplasms (BPTC) are reported here. Some cases had long-term follow-up. BPTC is a special type of primary breast neoplasm showing a triple-negative profile but low aggressive potential. Knowledge on BPTC is still scanty; therefore, the aim of the present paper was to report on the features of an additional 13 cases. All the patients were female individuals, and the mean age at presentation was 62.6 years; nodule sizes ranged from 0.6 to 2.5 cm (average, 1.6 cm). All the cases were characterized on histology by papillary, follicular as well as solid structures. The cells were columnar, eosinophilic mostly with granular cytoplasms, rich in mitochondria, with the features of oncocytes in no fewer than 7 cases. Estrogen and progesterone receptors as well as HER2 were consistently negative. The Ki67 proliferative index was low. Markers consistent with thyroid origin, such as TTF1 and thyroglobulin, were negative. Five cases stained for mammoglobin and GATA 3 were positive. All cases proved to be invasive and 2 cases each experienced metastases to 1 lymph node (axillary and intramammary). One case of the latter had a local recurrence. Nevertheless, all the patients are alive, free of disease 24 to 132 months after surgery, of which 8 are without further treatment The present series confirms that BPTC is a primary breast tumor of low malignant potential.

The management of lobular carcinoma in situ (LCIS). Is LCIS the same as ductal carcinoma in situ (DCIS)?

Lobular carcinoma in situ was first described over 60 years ago. Despite the long history, it continues to pose significant difficulties in screening, diagnosis, management and treatment. This is partly due its multi-focal and bilateral presentation, an incomplete understanding of its biology and natural history and perpetuation of misconceptions gathered over the last decades. In this review, the working group on behalf of EUSOMA has attempted to summarise the current thinking and management of this interesting lesion.