Maintenance of polarity and a dual cell population in adenoid cystic carcinoma of the breast: an immunohistochemical study

Re-evaluation of the myoepithelial cells roles in the breast cancer progression

Over the past decades, luminal epithelial cell lineage has gained considerable attraction as the functionally milk-secreting units and as the most fruitful acreage for breast cancer launching. Recognition of the effective involvement of the myoepithelial cells in mammary gland development and in hampering tumorigenesis has renewed the interest in investigating the biological roles of this second main mammary lineage. The human breast is made up of an extensively branching ductal system intervening by copious lobular units. The ductal system is coated by a chain of luminal epithelial cells (LECs) situated on a layer of myoepithelial cells (MECs) and encompassed by a distinguished basement membrane. Ductal contractility during lactation is a well-known function delivered by the MECs however this is not the only assignment mediated by these cellular populations. It has been well appreciated that the MECs exhibit a natural paracrine power in defeating cancer development and advancement. MECs were found to express numerous proteinase inhibitors, anti-angiogenic factors, and tumour suppressors proteins. Additionally, MECs contributed effectively to maintaining the right luminal cells' polarization and further separating them from the adjacent stroma by making an integrated fence. Indeed, disruption of the MECs layer was reported to facilitate the invasion of the cancer cells to the surrounding stroma. Nonetheless, MECs were also found to exhibit cancer-promoting effects and provoke tumour invasion and dissemination by displaying distinct cancer chemokines. Herein in this review, we aimed to address the roles delivered by MECs in breast cancer progression and decipher the molecular mechanisms regulating proper MECs' physiology, integrity, and terminal differentiation.

E-Cadherin Immunoreactivity in Canine Mammary Tumors

The reduction or loss of E-cadherin (E-cad), a calcium-dependent epithelial cell adhesion molecule, has been associated with tumor dedifferentiation and invasiveness. The immunohistochemical pattern of E-cad expression was evaluated in formalin-fixed and paraffin-embedded sections of 6 normal mammary glands, 3 dysplasias, 12 benign tumors (8 benign mixed tumors, 4 adenomas), and 60 malignant tumors (12 stage 0, 29 stage I, 19 stage II) of the canine mammary gland. E-cadherin expression was classified as membranous, when on cell–cell boundaries, or as cytoplasmic, when in the form of a diffuse cytoplasmic staining. In addition, the percentage of E-cad–positive epithelial neoplastic cells was graded by a semiquantitative method, categorizing cases into a reduced (or -) type group, when showing less than 25% positivity, a reduced (or +/-) type group, when showing 25–75% positivity, and a preserved (or +) type group, when more than 75% positive cells were present. In the normal mammary gland, E-cad expression was evident in epithelial luminal cells. A stronger positivity was revealed in ductular than in alveolar luminal cells. The myoepithelial cells showed inconsistent, weak cytoplasmic positivity in the normal gland as well as in mammary tumors. In normal glands and benign and malignant noninvasive tumors, E-cad expression was mainly membranous and preserved in most of the epithelial cells. In stage I tumors, both membranous (38%) and cytoplasmic (62%) positivity were well represented, as well as preserved type (55%) and reduced type (45%) tumors. All stage II malignant tumors showed the highest frequency of cytoplasmic positivity (79%) and reduced type (62%) tumors.

The unique luminal staining pattern of cytokeratin 5/6 in adenoid cystic carcinoma of the breast may aid in differentiating it from its mimickers

Adenoid cystic carcinoma (AdCC) of the breast is an uncommon but distinct neoplasm composed of a dual cell population polarized around true glandular (luminal) spaces and pseudolumina. The aim of this study was to clarify whether various immunohistochemical markers (CK7, EMA, CD117, p63, calponin, CD10, S100, CK5/6, CK14, vimentin, and type IV collagen) can distinguish between the two cell types in classical AdCC (n = 14) and in collagenous spherulosis (n = 5). The sensitivity and specificity of these 11 markers to distinguish luminal from abluminal cells were evaluated using a curve created by plotting the true-positive rate (sensitivity) against the false-positive rate (1 - specificity) at threshold settings of 0, 10, 50, and 70 %. The most sensitive and specific markers for luminal cells in AdCC were CK7 and EMA; those for abluminal cells were type IV collagen, p63, and vimentin. CD10 and S100 did not act as abluminal markers in AdCC. CK5/6, one of the basal/myoepithelial markers, was expressed more frequently in luminal than in abluminal cells of AdCC. Thus, CK5/6 immunostaining resulted in a reverse expression pattern, analogous to what we recently documented in clear cells in mammary adenomyoepithelioma. In conclusion, compared with myoepithelial/abluminal cells of normal breast or collagenous spherulosis, the neoplastic abluminal cells of classical AdCC are characterized by enhanced vimentin and attenuated CD10 and S100. Furthermore, the luminal cells of AdCC show a unique aberrant staining pattern for CK5/6 that may aid in the differential diagnosis.

Adenoid cystic carcinoma: triple negative breast cancer with good prognosis

Adenoid cystic carcinoma of the breast (ACCb) is a rare type of breast cancer. The treatment is not consensual. The authors report two cases of ACCb. Case 1: A 59-year-old woman with T1bN0M0, who went for lumpectomy and adjuvant radiation therapy (RT) (60 Gy in 30 fractions); Case 2: A 43-year-old woman, who went for modified radical mastectomy with T3N1M0, and underwent adjuvant chemotherapy, and a sequential regimen with antracyclin and taxane, prior to adjuvant RT (50 Gy/25 fractions).

Adenoid cystic carcinoma of breast: Recent advances

Adenoid cystic carcinoma (ACC) of the breast is a rare special subtype of breast cancer characterized by the presence of a dual cell population of luminal and basaloid cells arranged in specific growth patterns. Most breast cancers with triple-negative, basal-like breast features (i.e., tumors that are devoid of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 expression, and express basal cell markers) are generally high-grade tumors with an aggressive clinical course. Conversely, while ACCs also display a triple-negative, basal-like phenotype, they are usually low-grade and exhibit an indolent clinical behavior. Many discoveries regarding the molecular and genetic features of the ACC, including a specific chromosomal translocation t(6;9) that results in a MYB-NFIB fusion gene, have been made in recent years. This comprehensive review provides our experience with the ACC of the breast, as well as an overview of clinical, histopathological, and molecular genetic features.

K5/K14-positive cells contribute to salivary gland-like breast tumors with myoepithelial differentiation

Salivary gland-like tumors of the breast show a great variety of architectural patterns and cellular differentiations such as glandular, myoepithelial, squamous, and even mesenchymal phenotypes. However, currently little is known about the evolution and cellular differentiation of these tumors. For that reason, we performed an in situ triple immunofluorescence lineage/differentiation tracing (isTILT) and qRT-PCR study of basal (K5/K14), glandular (K7/K8/18), and epidermal-specific squamous (K10) keratins, p63, and smooth muscle actin (SMA; myoepithelial marker) with the aim to construct and trace different cell lineages and define their cellular hierarchy in tumors with myoepithelial differentiation. isTILT analysis of a series of 28 breast, salivary, and lacrimal gland tumors, including pleomorphic adenomas (n=8), epithelial-myoepithelial tumors (n=9), and adenoid cystic carcinomas (n=11) revealed that all tumor types contained K5/K14-positive progenitor cells in varying frequencies from a few percent up to 15%. These K5/K14-positive tumor cells were found to differentiate to glandular- (K8/18-positive) and myoepithelial-lineage (SMA-positive)-specific cells and were also shown to generate various heterologeous cell differentiations such as squamous and mesenchymal progenies. p63 was co-expressed with K5/K14 in basal-like progenitor cells, myoepithelial, and squamous cells but not in glandular cells. Our results show that the corresponding counterpart tumors of breast and salivary/lacrimal glands have identical cellular compositions. Taken together, our isTILT and RNA-expression data indicate that look-alike tumors of the breast represent a special subgroup of basal-type tumors with benign or usually low malignant potential.

Myoepithelial and epithelial-myoepithelial, mesenchymal and fibroepithelial breast lesions: updates from the WHO Classification of Tumours of the Breast 2012

In the 4th edition of the WHO Classification of Tumours of the Breast, myoepithelial lesions are retitled myoepithelial and epithelial-myoepithelial lesions in order to better reflect the dual participation of luminal and myoepithelial compartments in some key entities. Malignant myoepithelioma, described as a section within the chapter on myoepithelial lesions in the 3rd edition, is recognised in the 4th edition as part of metaplastic carcinoma. Adenomyoepithelioma with malignancy is categorised in terms of the cellular component undergoing malignant transformation. The list of antibodies that can be used for identifying myoepithelial cells is updated. Among mesenchymal lesions, new additions are nodular fasciitis and atypical vascular lesions, while the haemangiopericytoma is removed. The 3rd edition stated that pathological prediction of behaviour of phyllodes tumours is difficult in the individual case. In the 4th edition, some progress has been made in prioritisation and weighting of histological parameters that can potentially estimate probability of recurrence. The WHO Working Group advocates leaning towards a diagnosis of fibroadenoma in cases where there is histological uncertainty in distinction from a benign phyllodes tumour, or adopting the neutral term 'benign fibroepithelial neoplasm', as the clinical behaviour of fibroadenoma overlaps with that of benign phyllodes tumour. The 3rd edition terminology of 'periductal stromal sarcoma' is revised to 'periductal stromal tumour', akin to the widespread consensus to avoid the use of the term 'cystosarcoma' in the context of phyllodes tumours.

Adenoid cystic carcinomas of the breast have low Topo IIα expression but frequently overexpress EGFR protein without EGFR gene amplification

Adenoid cystic carcinoma of the breast is a rare subtype of breast cancer with basal-like features. Published studies on breast adenoid cystic carcinoma are limited, resulting in relatively scarce information on the value of predictive tumor markers. We studied 20 primary cases of adenoid cystic carcinoma of the breast for expression of estrogen receptor, progesterone receptor, androgen receptor, epidermal growth factor receptor, HER-2/neu, and topoisomerase IIα using immunohistochemistry and fluorescent in situ hybridization methods. Estrogen and progesterone receptor expression were detected in 1 case each. All tumors were uniformly negative for Her-2/neu expression. Androgen receptor and topoisomerase IIα expression were weakly positive in three cases and 7 cases, respectively. Epidermal growth factor receptor overexpression was detected in 13 cases (65% of all cases). Amplification of TOP2A or HER-2/neu gene was not detected in any of the cases. Our study shows that the majority of adenoid cystic carcinomas of the breast do not overexpress Her-2/neu, topoisomerase IIα, or estrogen receptor, and thus, they are unlikely to respond to therapies targeting these proteins. However, these tumors frequently over-express epidermal growth factor receptor, indicating a potential benefit from anti-epidermal growth factor receptor therapy for patients with advanced adenoid cystic carcinomas of the breast.

Expression of laminin 5 basement membrane components in invading and recurring adenoid cystic carcinoma of the head and neck

OBJECTIVE

Adenoid cystic carcinoma (ACC) of the head and neck grows slowly with structural differentiation, however, this tumor nevertheless also shows a highly invasive potential and a high recurrence rate. Extracellular matrices have been suggested to play an important role in the differentiation and growth of ACC. The aim of this study is to understand the roles of laminin 5 basement membrane (BM) components, including collagen IV and laminin gamma2 for the high degree of invasiveness and the recurrence of ACC.

METHODS

Collagen IV and laminin gamma2 were immunohistochemically localized in tissue sections from nine patients with ACCs.

RESULTS

Cribriform structures with pseudocysts were preserved in small invading tumor nests, and the expression of both of collagen IV and laminin gamma2 was observed in the inner border of the pseudocysts and the surrounding area of the tumor nests. In areas of perineural invasion, the BM components continued to be expressed around the long tumor nests. Recurrent tumors consisted of multiple small nests with a few tumor cell layers, and the expression of the BM components was observed on both the inside of the inner tumor cells and the outside of the outer tumor cells, which was an obviously different appearance from that of the primary tumor.

CONCLUSION

ACC appears to possibly grow and invade using the laminin 5 BM matrices while also preserving their differentiated architecture. The laminin 5 BM matrices might play an important role not only in the differentiation and growth, but also in the invasion and recurrence of ACC of the head and neck.

KIT is highly expressed in adenoid cystic carcinoma of the breast, a basal-like carcinoma associated with a favorable outcome

Recent biological studies have classified breast carcinomas into HER2-overexpressing, estrogen receptor-positive/luminal, basal- and normal-like groups. According to this new biological classification, the objectives of our study were to assess the clinical, morphologic and immunophenotypic characteristics of adenoid cystic carcinoma of the breast in order to classify this subtype of breast carcinoma. A total of 18 cases of adenoid cystic carcinoma were identified from the Institut Curie files. Clinical information was available for 16 patients with a median follow-up of 6.5 years. Morphologically, all tumors were graded according to the system defined by Kleer and Oberman (histologic and nuclear grade). Immunophenotype was assessed with anti-ER, PR, HER-2, KIT, basal (CK5/6) and luminal cytokeratins (CK8/18) and p63 antibodies. One out of 18 tumors was nuclear grade 1 (16%), nine were nuclear grade 2 (50%) and eight were nuclear grade 3 (44%). All cases were estrogen receptor, progesterone receptor and HER-2 negative. Epithelial cells were strongly positive around glandular lumina with one or both cytokeratins, identifying the coexistence of CK5/6+ cells, CK5/6 and CK8/18+ cells, CK8/18+ cells and p63+ cells. All cases (100%) were also KIT positive. In all, 15 patients were treated by surgery. Nine of them received adjuvant radiotherapy. Follow-up was available for 16 patients. In all, 14 patients were alive. Two of them, initially treated by surgery only, presented a local recurrence. Two patients died (one of them treated by radiation therapy only died from her disease). Our study shows that adenoid cystic carcinoma of the breast is a special, estrogen receptor, progesterone receptor, HER-2 negative and highly KIT-positive, basal-like breast carcinoma, associated with an excellent prognosis. This highly specific immunophenotype could be useful to differentiate adenoid cystic carcinoma of the breast from other subtypes of breast carcinoma such as cribriform carcinoma.

Immunoreactivity for c-kit and p63 as an adjunct in the diagnosis of adenoid cystic carcinoma of the breast

Adenoid cystic carcinoma of the breast represents a unique clinicopathologic entity with a variable histological appearance and a relatively indolent clinical course in most of the cases. Adenoid cystic carcinoma may be difficult to differentiate from infiltrating duct carcinomas, and in particular from tubular and cribriform carcinomas, especially in core or vacuum-assisted biopsies. We evaluated the prevalence of c-kit, p63, and e-cadherin immunoreactivity in a series of 20 adenoid cystic carcinomas, comparing the results with those obtained in a series of infiltrating tubular carcinomas and infiltrating cribriform carcinomas. The hormone receptor status, proliferation labeling index, and HER/2 immunoreactivity had been previously investigated in all the cases. Three (15%) adenoid cystic carcinomas and all infiltrating tubular and cribriform carcinomas showed estrogen receptor and/or progesterone receptor immunoreactivity (P < 0.00001 for estrogen and P = 0.00002 for progesterone receptors). Adenoid cystic carcinomas consistently lacked any immunoreactivity for HER/2, whereas three (15%) infiltrating and cribriform carcinomas showed weak and incomplete membrane staining (P = 0.23077). Membranous immunoreactivity for c-kit was found in all except one (predominantly basaloid) adenoid cystic carcinomas (95%), and in none of the infiltrating tubular and cribriform carcinomas (P < 0.00001). Nuclear immunoreactivity for p63 was found in all except three (predominantly basaloid) adenoid cystic carcinomas (85%) and in none of the infiltrating tubular and cribriform carcinomas (P < 0.00001). All infiltrating tubular and cribriform carcinomas and 18/20 (90%) adenoid cystic carcinomas showed immunoreactivity for e-cadherin (P = 0.48718). In summary, adenoid cystic carcinomas showed the following phenotype: estrogen receptor-/progesterone receptor-/c-kit+/p63+ (13 cases, 65%), estrogen receptor-/progesterone receptor/c-kit+/p63- (three cases, 15%), estrogen receptor-/progesterone receptor-/c-kit-/p63+ (one case, 5%), estrogen receptor+/progesterone receptor+/c-kit+/p63+ (two cases, 10%), and estrogen receptor+/progesterone receptor-/c-kit+/p63+ (one case). By contrast, all the infiltrating tubular and cribriform carcinomas showed the estrogen receptor+/progesterone receptor+/c-kit-/p63- phenotype. Our data provide evidence that immunoreactivity for c-kit and/or p63 may be useful in differentiating adenoid cystic carcinomas from other types of breast cancer.

Myoepithelial cells: their origin and function in breast morphogenesis and neoplasia

The human breast epithelium is a branching ductal system composed of an inner layer of polarized luminal epithelial cells and an outer layer of myoepithelial cells that terminate in distally located terminal duct lobular units (TDLUs). While the luminal epithelial cell has received the most attention as the functionally active milk-producing cell and as the most likely target cell for carcinogenesis, attention on myoepithelial cells has begun to evolve with the recognition that these cells play an active part in branching morphogenesis and tumor suppression. A major question that has been the subject of investigation pertains to how the luminal epithelial and myoepithelial lineages are related and precisely how they arise from a common putative stem cell population within the breast. Equally important is the question of how heterotypic signaling occurs between luminal epithelial and surrounding myoepithelial cells in normal breast morphogenesis and neoplasia. In this review we discuss data from our laboratories and from others regarding the cellular origin of human myoepithelial cells, their function in maintaining tissue polarity in the normal breast, and their role during neoplasia.

The potential role of breast conservation surgery and adjuvant breast radiation for adenoid cystic carcinoma of the breast

PURPOSE

Adenoid cystic carcinoma (ACC) of the breast is a rare breast cancer variant and optimal management is unclear. A review of this unusual tumour was performed at our Institution, to assess the role of breast conservation in the management of this disease.

METHODS AND MATERIALS

A review of all cases of ACC of breast (1960-2000) treated at Princess Margaret Hospital (PMH) was undertaken. Information was collected on age at diagnosis, presenting features, tumour size and treatment modalities. Treatment outcomes were evaluated.

RESULTS

Eighteen female and one male patient were identified. Median age at diagnosis was 58 years (range 35-76 years). Four patients had lymph-node positive disease at presentation; the single male patient presented with metastatic disease. Surgery was either a lumpectomy (10 cases) or a simple, radical or modified radical mastectomy (9 patients). Nine of 19 patients received adjuvant radiotherapy (RT). The median follow-up time was 14 years; the recurrence rate at 10 years was 31% (95% CI 7-54%) with a range in time of recurrence from 2.3 to 11.9 years. Seven recurrences were identified (4 local, 1 regional, 2 metastatic). Two of these patients developed metastatic spread and died. Six of the 19 cases went on to develop second malignancies of whom four died. Among the 18 female patients, the 10-year overall (OS), cause-specific (CSS), and relapse free survival (RFS) rates were 75, 100, and 46% respectively.

CONCLUSIONS

ACC of the breast has a relatively prolonged natural history, and responds well to conservative management at presentation, with good outcome, even following local recurrence.

Microglandular adenosis with transition into adenoid cystic carcinoma of the breast

Microglandular adenosis (MGA) is a well-recognized, if rare and incompletely characterized, entity in which carcinoma is rarely thought to develop. We report 17 cases in which patterns of adenoid cystic carcinoma (ACC) coexisted with MGA. Immunocharacterization with beta-catenin, E-cadherin, cytokeratins (AE1/AE3), epithelial membrane antigen, S-100 protein, smooth muscle actin, and vimentin was also performed. Most cases had areas of invasive ACC characterized by its defining dual-lumen types. Some cases of ACC appeared to have expanded glands intermingled within the MGA, whereas in other cases ACC formed a transition with the characteristic small, gland-like spaces of MGA. MGA and "atypical MGA" stained irregularly and similarly to that seen in myoepithelium with the three markers of myoepithelial cells in breast: S-100 protein, smooth muscle actin, and vimentin. These markers were also positive in the more solid elements of the ACC. Our study suggests that ACC may develop in a background of and in continuity with MGA. Altered myoepithelial cells appear to be the major neoplastic element in both ACC and "atypical MGA." "Atypical MGA" with transition to ACC may show histologic patterns and an immunohistochemical profile similar to that of ACC. These lesions might be best interpreted as ACC in situ. Both MGA and ACC of the breast grow in an expansile and diffusely infiltrative pattern without having significant metastatic capacity. Their unusual interaction with the surrounding stroma may play a role in this benign biologic behavior.

To create the correct microenvironment: three-dimensional heterotypic collagen assays for human breast epithelial morphogenesis and neoplasia

The normal human breast comprises an inner layer of luminal epithelial cells and an outer layer of myoepithelial cells separated from the connective tissue stroma by an intact basement membrane. In breast cancer, tumor cells are in direct contact with the surrounding highly activated collagenous stroma, with little or no discernible myoepithelial fence from the original double-layered structure. To understand the evolution of these two scenarios, we took advantage of a three-dimensional hydrated collagen gel approach. The contribution of myoepithelial cells to normal morphogenesis was studied by ablation and rescue experiments, and genes regulated on tumor cell-fibroblast interaction were identified in a tumor environment assay. In normal breast morphogenesis, the ability to correctly polarize sialomucin to the luminal membrane of emerging acini was used as a criterion for apical polarity and functional differentiation. In the assay of breast neoplasia, the consequence of reciprocal tumor cell-fibroblast interaction was addressed morphologically as well as by a differential display approach. Normal breast epithelial cells were purified immunomagnetically and an established cell line, MCF-7, was used as a surrogate tumor cell. With regard to the importance of myoepithelial cells in normal breast epithelial morphogenesis, the collagen gel assay elucidated the following subtleties: In contrast to culturing in basement membrane gels, luminal epithelial cells when cultured alone made structures that were all inversely polarized. This aberrant polarity could be rescued by co-culture with myoepithelial cells. The molecular activity of myoepithelial cells responsible for correct morphogenesis was narrowed down to the laminin-1 component of the basement membrane. As for the consequence of interaction of tumor cells with connective tissue fibroblasts, the assay allowed us to identify a hitherto undescribed gene referred to as EPSTI1. The relevance of the assay-based identification of regulated genes was confirmed in a series of breast carcinomas in which EPSTI1 was highly upregulated compared with normal breast. Few if any of these observations would have been possible on two-dimensional tissue culture plastic.

Salivary gland-like tumours of the breast: surgical and molecular pathology

Breast glands and salivary glands are tubulo-acinar exocrine glands that can manifest as tumours with similar morphological features, but that differ in incidence and clinical behaviour depending on whether they are primary in breast or salivary glands. Salivary gland-like tumours of the breast are of two types: tumours with myoepithelial differentiation and those devoid of myoepithelial differentiation. The first and more numerous group comprises a spectrum of lesions ranging from "bona fide" benign (such as benign myoepithelioma and pleomorphic adenoma), to low grade malignant (such as adenoid cystic carcinoma, low grade adenosquamous carcinoma, and adenomyoepithelioma), to high grade malignant lesions (malignant myoepithelioma). The second group comprises lesions that have only recently been recognised, such as acinic cell carcinoma, oncocytic carcinoma of the breast, and the rare mucoepidermoid carcinoma.

Solid variant of mammary adenoid cystic carcinoma with basaloid features: a study of nine cases

Adenoid cystic carcinoma of the breast is a rare neoplasm that represents <1% of breast carcinomas. The tumors are histologically indistinguishable from examples in other sites, and they have a generally favorable prognosis. Several studies have investigated the possible correlation between histologic grade in adenoid cystic carcinoma (largely determined by cytology and growth pattern) and prognosis. Some earlier reports concluded that a solid variant of mammary adenoid cystic carcinoma had a more aggressive clinical course, but others did not confirm this impression. This report describes nine patients with a solid variant of mammary adenoid cystic carcinoma that has a striking basaloid appearance. All were women ranging in age from 37 to 83 years. A solitary mass was evident in all patients. Tumor size was 1.1-15 cm (mean 3.7 cm). The tumors exhibited a predominantly solid architecture comprised of basaloid appearing cells with moderate to marked nuclear atypia. Five tumors had >5 mitotic figures per 10 high power microscopic fields. Intercalated ducts were found in all tumors, being well formed in six and poorly formed in three. Immunohistochemical stains for cytokeratins, basement membranes, and vimentin were consistently positive. Surgery was performed in all cases consisting of excision in seven and mastectomy in two. Axillary lymph node metastases were found in two of six axillary dissections and four had negative lymph nodes. The lymph nodes were not examined in three patients. Follow-up information was available for seven patients. Six women had no evidence of disease after follow-up of 2-88 months (mean 32 months), one patient died of unknown causes, and one patient was lost to follow-up. It is concluded that the solid variant of mammary carcinoma with basaloid features is a histologically distinct tumor that is capable of axillary metastases. Long-term follow-up of a larger series of cases will be needed to determine whether the prognosis of these patients differs significantly from that of women with conventional adenoid cystic carcinoma. Presently, these patients are candidates for axillary staging by sentinel lymph node mapping or low axillary dissection if there is no clinical evidence of axillary metastases. Systemic adjuvant treatment would be prudent when axillary nodal metastases are present. Breast-conserving surgery with radiation is an option if negative margins can be achieved because this appears to be a unicentric form of carcinoma.

Normal and tumor-derived myoepithelial cells differ in their ability to interact with luminal breast epithelial cells for polarity and basement membrane deposition

The signals that determine the correct polarity of breast epithelial structures in vivo are not understood. We have shown previously that luminal epithelial cells can be polarized when cultured within a reconstituted basement membrane gel. We reasoned that such cues in vivo may be given by myoepithelial cells. Accordingly, we used an assay where luminal epithelial cells are incorrectly polarized to test this hypothesis. We show that culturing human primary luminal epithelial cells within collagen-I gels leads to formation of structures with no lumina and with reverse polarity as judged by dual stainings for sialomucin, epithelial specific antigen or occludin. No basement membrane is deposited, and β4-integrin staining is negative. Addition of purified human myoepithelial cells isolated from normal glands corrects the inverse polarity, and leads to formation of double-layered acini with central lumina. Among the laminins present in the human breast basement membrane (laminin-1, -5 and -10/11), laminin-1 was unique in its ability to substitute for myoepithelial cells in polarity reversal.

Myoepithelial cells were purified also from four different breast cancer sources including a biphasic cell line. Three out of four samples either totally lacked the ability to interact with luminal epithelial cells, or conveyed only correction of polarity in a fraction of acini. This behavior was directly related to the ability of the tumor myoepithelial cells to produce α-1 chain of laminin. In vivo, breast carcinomas were either negative for laminin-1 (7/12 biopsies) or showed a focal, fragmented deposition of a less intensely stained basement membrane (5/12 biopsies). Dual staining with myoepithelial markers revealed that tumor-associated myoepithelial cells were either negative or weakly positive for expression of laminin-1, establishing a strong correlation between loss of laminin-1 and breast cancer. We conclude that the double-layered breast acinus may be recapitulated in culture and that one reason for the ability of myoepithelial cells to induce polarity is because they are the only source of laminin-1 in the breast in vivo. A further conclusion is that a majority of tumor-derived/-associated myoepithelial cells are deficient in their ability to impart polarity because they have lost their ability to synthesize sufficient or functional laminin-1. These results have important implications for the role of myoepithelial cells in maintenance of polarity in normal breast and how they may function as structural tumor suppressors.

Lactation affects expression of intermediate filaments in human breast epithelium

The human breast contains two epithelial lineages, luminal epithelial and myoepithelial. Specific patterns of expression of intermediate filaments have previously been demonstrated in the resting breast. To determine how terminal differentiation and lactation influenced expression of intermediate filaments in breast epithelial cells, we used Western blot analysis to measure the levels of vimentin, alpha-smooth muscle actin, keratin 14, and keratin 18 in the resting and lactating breast. Confocal immunofluorescence was used to determine the subcellular site of localization of the intermediate filaments. Vimentin was localised to myoepithelial cells in both the resting and lactating gland. There was a four-fold increase in vimentin protein levels in lactating tissue relative to resting tissue, and this may be related to increased cellular activity of the myoepithelial cells which surround secretory alveoli. Alpha-smooth muscle actin and keratin 14 were detected in myoepithelial cells, and similar levels of expression were found in lactating and resting tissue. In the resting breast, keratin 18 and keratin 8 were detected in luminal epithelial cells in a filamentous form, whereas in lactating tissue it was present in a punctate form in luminal cells and also seen as granules in the lumen of alveoli. Our results indicate that intermediate filament expression patterns are altered in the lactating human breast, and this may reflect their role in the fully functional gland.

Adenoid cystic carcinoma of the breast: a tumour commonly devoid of oestrogen receptors and related proteins

AIM

Adenoid cystic carcinoma (ACC) of the breast is an uncommon well-differentiated tumour with good prognosis, and sometimes difficult to distinguish from in-situ and invasive cribriform carcinoma (ICC) which are relatively more common. Recently, we encountered a case of ACC that proved to be totally oestrogen receptor (ER) negative by immunohistochemistry. We investigated the possibility that this may be a consistent feature that can help in differentiating ACC from ICC which are usually ER positive.

METHODS AND RESULTS

The immunoperoxidase technique was used to study the expression of ER and other related proteins in six cases of ACC and two cases of ICC. All ACC cases were negative for oestrogen (ER) and progesterone (PgR) receptors whereas the two ICC were strongly positive for ER and showed a variable degree of PgR positivity. In addition, ACC cases were pS2 negative and showed minimal expression of prolactin receptors (PrlR), while the two ICC showed widespread and strong staining for pS2 and PrlR. The percentages of cells staining positively for Ki67 and p27 were generally lower in ACC than in ICC. Both tumour types were c-erbB-2 negative, but p53 was weakly to moderately positive.

CONCLUSIONS

The findings suggest that a negative immunoperoxidase staining for ER would confirm the diagnosis of ACC in contrast to the positive staining which is always seen in ICC. The findings also raise the issue of the presence of a specific class of ER negative breast carcinomas which are negative not because of poor differentiation, but because of their derivation from, or differentiation along, an ER negative cell lineage.