Myoepithelial carcinoma arising in an adenomyoepithelioma of the breast: Case report with immunohistochemical and mutational analysis

Adenomyoepithelioma (AME) of the breast is an uncommon tumor characterized by biphasic proliferation of both epithelial and myoepithelial cells. In rare instances, the epithelial, the myoepithelial or both components of an AME may become malignant. Described herein is the case of a 69-year-old woman who presented with myoepithelial carcinoma of the breast in an AME. Malignancy of myoepithelial component (MEC) was evidenced by the presence of cytological atypia, high mitotic rate, necrosis and local invasion. Immunohistochemical study demonstrated strong expression of P53 and phosphorylated extracellular signal-regulated kinase 1/2 in MEC. Laser capture microdissection technique and mutational analysis further revealed point mutation of the p53 gene (T-->G transversion at codon 270) in this population, but not in glandular epithelial cells or adjacent normal ductal epithelium. No mutations in exons 1 and 2 of the K-, H-, and N-ras genes were identified in any of the neoplastic component. To the authors' knowledge this is the first report of a mutation in the p53 gene in a malignant AME of the breast.

[Immunohistochemical characterization of salivary gland tumors with tissue micro-arrays]

Systematic analysis of gene expression in salivary gland tumors is necessary to identify genes associated with specific tumor types. From the salivary gland register of the University Hospital Hamburg-Eppendorf sufficient samples of various tumors were available to generate Tissue Micro-Arrays (TMA). In light of the considerable heterogeneity of salivary gland tumors, this study was aimed at evaluating the suitability of TMA in salivary gland diagnostics and research. Epithelial antigens are not sufficient for a tumor-type-specific characterization. Myoepithelial markers are suitable for distinguishing biphasic tumor types from purely epithelial tumors. The detection of amylase in acinic cell carcinomas, and the detection of steroid hormone receptors in these and other malignant salivary gland tumors particularly in combination with the expression of transcription factors, oncogenes and proliferation associated antigens result in characteristic expression profiles. These may prove to be valuable for further investigations, especially on the molecular level.

Cytokinesis failure generating tetraploids promotes tumorigenesis in p53-null cells

A long-standing hypothesis on tumorigenesis is that cell division failure, generating genetically unstable tetraploid cells, facilitates the development of aneuploid malignancies. Here we test this idea by transiently blocking cytokinesis in p53-null (p53-/-) mouse mammary epithelial cells (MMECs), enabling the isolation of diploid and tetraploid cultures. The tetraploid cells had an increase in the frequency of whole-chromosome mis-segregation and chromosomal rearrangements. Only the tetraploid cells were transformed in vitro after exposure to a carcinogen. Furthermore, in the absence of carcinogen, only the tetraploid cells gave rise to malignant mammary epithelial cancers when transplanted subcutaneously into nude mice. These tumours all contained numerous non-reciprocal translocations and an 8-30-fold amplification of a chromosomal region containing a cluster of matrix metalloproteinase (MMP) genes. MMP overexpression is linked to mammary tumours in humans and animal models. Thus, tetraploidy enhances the frequency of chromosomal alterations and promotes tumour development in p53-/- MMECs.

Myoepitheliale Tumoren der Kopfspeicheldrüsen

This tutorial focuses on myoepithelial tumors of salivary glands, an entity with heterogeneous cytomorphology and inconsistent immunophenotype. Moreover, the clinical course cannot be predicted reliably from cytomorphological and immunophenotypic analysis. This heterogeneity causes problems in routine diagnostic, so that diagnosis ultimately rests on conventional histology. In a representative series of myoepitheliomas and malignant myoepitheliomas, antibodies against cytokeratins 5/6, S 100 protein and vimentin produced the most consistent reactivity profile. Staining for cytokeratins 5/6 is a useful addition to the established immunohistologic marker panel in the work-up of myoepitheliomas, because of its reliable expression in most cases and because it may underline the epithelial nature of the lesion. Comparative genomic hybridisation (CGH) profiles of myoepitheliomas and myoepithelial carcinomas showed no chromosomal aberration in less than 50% of myoepithelial carcinomas, so that CGH is of limited help in a given case. In a case that was represented in three separately localized manifestations of the disease that differed in their CGH profiles, gross genetic aberrations suggest to be acquired during tumor progression and should raise the suspicion of malignancy. Thus, diagnosis of myoepithelial tumors of salivary glands has to rest on morphological grounds with support of a restricted panel of immunohistologic markers.

[Myoepithelioma of soft tissue -- case report with clinicopathologic, ultrastructural, and cytogenetic findings]

The case of a soft tissue myoepithelioma is presented including clinicopathologic, ultrastructural, and genetic findings. A 30-year-old male patient suffered from a soft tissue tumor within the deep soft tissues of the right lower leg measuring 13.2 x 8.2 x 9 cm. Histologically, the lesion was diagnosed as a myoepithelioma displaying a lobulated architecture with cords and nests of epithelioid and spindle cells without cytologic atypia lying within a fibromyxoid and partly chondroid matrix; immunohistochemistry was positive for pancytokeratin, S100-protein, calponin and partly for GFAP and EMA. Ultrastructural analysis revealed glycogen deposits and cell-membrane-associated plaque structures, whereas true myofilaments could not be identified (with immunohistochemistry being negative for actin). Using comparative genomic hybridization (CGH), a gain of chromosome Y was detected. A loss on 17p could not be detected unambiguously. However, based on the low resolution of CGH a small loss cannot be excluded. The patient was free of disease 25 months following complete tumor resection. Myoepitheliomas/mixed tumors of deep soft tissue represent rare soft tissue lesions that may reach a considerable size and may mimic other soft tissue tumors or sarcomas. Based on a local relapse rate of approximately 20% according to the literature, a complete resection with thorough follow-up should be recommended.

Gene expression profile of an adenomyoepithelioma of the breast with a reciprocal translocation involving chromosomes 8 and 16

Myoepithelium is an integral part of the mammary ductal and lobular architecture, positioned between luminal cells and the basement membrane. We describe the first report on cytogenetic findings in an adenomyoepithelioma of the breast with a balanced t(8;16)(p23;q21), and provide gene expression profile using Affymetrix GeneChip U95AV2 (Affymetrix, Santa Clara, CA). Differential analysis identified 857 genes with 2-fold or more mRNA change in comparison to pooled normal breast control; immunohistochemical analysis was used to confirm these results in a limited number of genes. Expression results were grouped based on the chromosomal location of the genes and associated protein function, and identified several potential pathogenetic mechanisms (autocrine and paracrine growth stimuli) in the development of myoepithelial tumors.

Expression of ATM, p53, and the MRE11-Rad50-NBS1 complex in myoepithelial cells from benign and malignant proliferations of the breast

AIMS

To analyse the expression of proteins involved in DNA double strand break detection and repair in the luminal and myoepithelial compartments of benign breast lesions and malignant breast tumours with myoepithelial differentiation.

METHODS

Expression of the ataxia telangiectasia (ATM) and p53 proteins was immunohistochemically evaluated in 18 benign and malignant myoepithelial tumours of the breast. Fifteen benign breast lesions with prominent myoepithelial compartment were also evaluated for these proteins, in addition to those in the MRE11-Rad50-NBS1 (MRN) complex, and the expression profiles were compared with those seen in eight independent non-cancer (normal breast) samples and in the surrounding normal tissues of the benign and malignant tumours examined.

RESULTS

ATM expression was higher in the myoepithelial compartment of three of 15 benign breast lesions and lower in the luminal compartment of eight of these lesions compared with that found in the corresponding normal tissue compartments. Malignant myoepithelial tumours overexpressed ATM in one of 18 cases. p53 was consistently negative in benign lesions and was overexpressed in eight of 18 malignant tumours. In benign breast lesions, expression of the MRN complex was significantly more reduced in myoepithelial cells (up to 73%) than in luminal cells (up to 40%) (p=0.0005).

CONCLUSIONS

Malignant myoepithelial tumours rarely overexpress ATM but are frequently positive for p53. In benign breast lesions, expression of the MRN complex was more frequently reduced in the myoepithelial than in the luminal epithelial compartment, suggesting different DNA repair capabilities in these two cell types.

Malignant myoepithelial cells are associated with the differentiated papillary structure and metastatic ability of a syngeneic murine mammary adenocarcinoma model

BACKGROUND

The normal duct and lobular system of the mammary gland is lined with luminal and myoepithelial cell types. Although evidence suggests that myoepithelial cells might suppress tumor growth, invasion and angiogenesis, their role remains a major enigma in breast cancer biology and few models are currently available for exploring their influence. Several years ago a spontaneous transplantable mammary adenocarcinoma (M38) arose in our BALB/c colony; it contains a malignant myoepithelial cell component and is able to metastasize to draining lymph nodes and lung.

METHODS

To characterize this tumor further, primary M38 cultures were established. The low-passage LM38-LP subline contained two main cell components up to the 30th subculture, whereas the higher passage LM38-HP subline was mainly composed of small spindle-shaped cells. In addition, a large spindle cell clone (LM38-D2) was established by dilutional cloning of the low-passage MM38-LP cells. These cell lines were studied by immunocytochemistry, electron microscopy and ploidy, and syngeneic mice were inoculated subcutaneously and intravenously with the different cell lines, either singly or combined to establish their tumorigenic and metastatic capacity.

RESULTS

The two subpopulations of LM38-LP cultures were characterized as luminal and myoepithelium-like cells, whereas LM38-HP was mainly composed of small, spindle-shaped epithelial cells and LM38-D2 contained only large myoepithelial cells. All of them were tumorigenic when inoculated into syngeneic mice, but only LM38-LP cultures containing both conserved luminal and myoepithelial malignant cells developed aggressive papillary adenocarcinomas that spread to lung and regional lymph nodes.

CONCLUSION

The differentiated histopathology and metastatic ability of the spontaneous transplantable M38 murine mammary tumor is associated with the presence and/or interaction of both luminal and myoepithelial tumor cell types.

Cytogenetic analysis of myoepithelial cell carcinoma of salivary gland

Myoepithelial cell carcinoma (MCC) of the salivary gland is a rare entity. Here, we describe the karyotype of MCC. The patient was a 53-year-old man, with a rapidly growing lesion of the palate. Despite complete surgical excision, radio- and chemotherapy, the lesion rapidly harboured local and distant metastases leading to the death of the patient, 4 months after the diagnosis. On histological and ultrastructural examination, the primary tumour and the related metastases were composed of oval and spindle cells, with features of myoepithelial cell differentiation reported in the literature. Cytogenetic analysis showed a composite karyotype in the primary tumour: 45-46,XY, +3[cp3]/ 44-45,XY, -17[cp4]/ 46,XY[5]. The lymph-node metastasis was near-triploid and showed a complex karyotype. Our cytogenetic data differ from those described in benign or slowly growing salivary gland tumours showing myoepithelial cell differentiation. It is suggested that highly aggressive tumours might follow a different pathway of malignant transformation.

[Poorly differentiated breast carcinoma with an abundant myoepithelial component: morphologic and immunohistochemical features and mammaglobin gene expression ]

In this report, we describe a case of poorly differentiate myoepithelial cell rich carcinoma in with morphological findings of large poligonal nests with festoon-like pattern sometimes showing central necrosis, reminiscent of a comedo-like pattern and numerous mitoses. Immunohistochemical staining shows positive reaction for cytokeratin AE/1, CAM 5.2, 34 beta E12, vimentin, smooth muscle actin, EMA, S100 protein and oncogene cERB.b2 and negative for estrogen, progesterone, GFAP and chromogranin. Moreover, this carcinoma show the expression of the mammaglobin mRNA, a highly specific marker of breast epithelial cells that it is not expressed in all breast carcinoma.

Analysis of the tumour suppressor genes, FHIT and WT-1, and the tumour rejection genes, BAGE, GAGE-1/2, HAGE, MAGE-1, and MAGE-3, in benign and malignant neoplasms of the salivary glands

AIMS

Molecular genetic changes involved in tumorigenesis and malignant transformation of human tumours are novel targets of cancer diagnosis and treatment. This study aimed to analyse the expression of putative tumour suppressor genes, FHIT and WT-1, and tumour rejection genes, BAGE, GAGE-1/2, MAGE-1, MAGE-3, and HAGE (which are reported to be important in human cancers), in salivary gland neoplasms.

METHODS

Gene expression was analysed by reverse transcription polymerase chain reaction (RT-PCR) in normal salivary gland tissue and 44 benign and malignant salivary gland tumours.

RESULTS

Aberrant FHIT transcripts were found in one of 38 normal salivary glands, three of 28 adenomas, and two of 16 carcinomas. WT-1 mRNA was detectable in two adenomas and five carcinomas. Immunoblotting showed that WT-1 mRNA expression was associated with raised WT-1 protein concentrations. RT-PCR for detection of BAGE, GAGE, and MAGE gene expression was positive in two adenomas and nine carcinomas, but negative in normal salivary gland tissue. HAGE mRNA was found in two normal salivary glands, 11 benign, and eight malignant tumours.

CONCLUSIONS

FHIT mRNA splicing does not appear to be involved in the genesis of salivary gland neoplasms. The upregulation of WT-1 mRNA in tumours of epithelial/myoepithelial phenotype may imply a potential role of WT-1 in the genesis and/or cellular differentiation of these salivary gland tumours. The tumour rejection genes were more frequently, but not exclusively, expressed in malignant salivary gland tumours than in benign neoplasms, although none was suitable as a diagnostic marker of malignancy in salivary gland neoplasms.

Epithelial-myoepithelial carcinoma of the parotid gland-evidence of contrasting DNA patterns in two different histological parts

Epithelial-myoepithelial carcinoma (EMC) is a rare neoplasm arising predominantly in the salivary glands, in particular in the parotid gland. We report the morphological features of an epithelial-myoepithelial carcinoma of the parotid gland with one lymph-node metastasis including a molecular genetic study of this tumor. Immunohistochemical and ultrastructural results confirmed the epithelial-myoepithelial dualism of the carcinoma. The loss of heterozygosity (LOH) analysis revealed different LOH results for the solid and the tubular growth pattern of the primary tumor, but showed identical findings for the solid primary tumor component and the lymph node metastasis which had also a solid appearance. LOH could be demonstrated in the whole primary tumor at D13S217 (13q12) and D18S58 (18q21). In three other microsatellite loci [D9S162 (9p22-p21), D10S251 and D10S541 (surrounding the PTEN/MMAC1 gene on 10q23-q24)], clearly recognizable LOH was found in the solid part and in the metastasis, whereas the tubular component demonstrated only a slight decrease of the same allele. No mutation or methylation of the p16 gene or alteration of the PTEN/MMAC1 gene could be found. Nevertheless, our results provoke a discussion, whether these genetic alterations could be considered as determinants of histologically and prognostically divergent types in EMC.

Myoepithelial mRNA expression profiling reveals a common tumor-suppressor phenotype

A series of myoepithelial cell lines and xenografts derived from benign human myoepithelial tumors of diverse sources (salivary gland, breast, and lung) exhibit common mRNA expression profiles indicative of a tumor-suppressor phenotype. Previously established myoepithelial cell lines and xenografts (HMS-#; HMS-#X) were compared to nonmyoepithelial breast carcinoma cells (MDA-MB-231 and MDA-MB-468, and inflammatory breast carcinoma samples, IBCr, and IBCw), a normal mammary epithelial cell line (HMEC) and individual cases of human breast cancer (zcBT#T), and matched normal human breast tissues (zcBT#N) (overall samples = 22). The global gene expression profile (22,000 genes) of these individual samples was examined using Affymetrix Microarray Gene Chips and subsequently analyzed with both Affymetrix and DChip algorithms. The myoepithelial cell lines/xenografts were distinct and very different from the nonmyoepithelial breast carcinoma cells and the normal breast and breast tumor biopsies. Two hundred and seven specifically selected genes represented a subset of genes that distinguished (P < 0.05) all the myoepithelial cell lines/xenografts from all the other samples and which themselves exhibited hierarchical clustering. Further analysis of these genes revealed increased expression in genes belonging to the classes of extracellular matrix proteins, angiogenic inhibitors, and proteinase inhibitors and decreased expression belonging to the classes of angiogenic factors and proteinases. Developmental genes were also differentially expressed (either over or underexpressed). These studies confirm our previous impression that human myoepithelial cells express a distinct tumor-suppressor phenotype.

Relative paucity of gross genetic alterations in myoepitheliomas and myoepithelial carcinomas of salivary glands

The diagnosis of salivary gland myoepithelioma, an entity with heterogeneous cytomorphology and inconsistent immunophenotype, rests on conventional histology. However, the clinical course cannot be predicted reliably from cytomorphological and immunophenotypic analysis. The present study determined the immunophenotype of a representative series of 12 myoepitheliomas and 21 malignant myoepitheliomas. Among the seven markers tested, antibodies against cytokeratins 5/6, S-100 protein, and vimentin produced the most consistent reactivity profile. Comparative genomic hybridization (CGH) profiles of 12 myoepitheliomas showed chromosomal losses in three of 12 cases. In myoepithelial carcinomas, however, ten of 19 tissues investigated by CGH lacked detectable cytogenetic aberrations. In five cases, aberrations involved chromosome 8, in line with observations in salivary gland carcinomas of other differentiation. One case that was represented in three separately localized manifestations of the disease proved informative as to the relevance of gross aberration for tumour development, as these tumours differed in their CGH profiles. Staining for cytokeratins 5/6 is a useful addition to the established immunohistological marker panel in the work-up of myoepitheliomas, because of its reliable expression in most cases and because it may underline the epithelial nature of the lesion. CGH proved to be of limited value as a diagnostic adjunct; the presence of numerous gross cytogenetic aberrations should raise the suspicion of malignancy. The low frequency of aberrations detectable by CGH in overtly malignant myoepithelial neoplasms suggests that gross cytogenetic alterations were acquired in the course of tumour progression and points to the relevance of genetic changes not resolved by CGH.

A case of myoepithelial carcinoma displaying biallelic inactivation of the tumour suppressor gene APC in a patient with familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant disorder caused by mutation of the APC gene. It is characterised by the appearance of hundreds to thousands of colorectal adenomas in adolescence and the subsequent development of colorectal cancer. Various extracolonic malignancies are associated with FAP, including desmoids and neoplasms of the stomach, duodenum, pancreas, liver, and brain. We present a family affected by FAP with an exon 14 APC mutation displaying two rare extracolonic lesions, a hepatoblastoma and a myoepithelial carcinoma. The hepatoblastoma was found in a male patient aged 2 years. The second lesion, a myoepithelial carcinoma of the right cheek, was found in a female patient aged 14 years. Inactivation of the normal APC allele was demonstrated in this lesion by loss of heterozygosity analysis, thus implicating APC in the initiation or progression of this neoplasm. This is the first reported case of this lesion in a family affected by FAP.

Telomere length and telomerase activity in canine mammary gland tumors

OBJECTIVE

To measure telomere length and telomerase activity in naturally occurring canine mammary gland tumors.

SAMPLE POPULATION

27 mammary gland tumor specimens obtained during resection or necropsy and 12 mammary gland tissue specimens obtained from healthy (control) dogs.

PROCEDURE

Telomere length in tissue specimens was measured by use of restriction endonuclease digestion and Southern blot analysis. Telomerase activity was measured by use of a telomeric repeat amplification protocol assay.

RESULTS

Telomere length in mammary gland tumors ranged from 11.0 to 21.6 kilobase pairs (kbp; mean +/- SEM, 14.5+/-0.5 kbp) but did not differ among tumor types. Telomeres in mammary gland tumors were slightly shorter than in normal tissue specimens, but telomere length could not be directly compared between groups, because mean age of dogs was significantly different between groups. Age was negatively correlated with telomere length in control dogs but was not significantly correlated with length in affected dogs. Telomerase activity was detected in 26 of 27 mammary gland tumors and in 4 of 12 normal tissue specimens. However, telomerase activity and telomere length were not correlated in tumor specimens.

CONCLUSIONS AND CLINICAL RELEVANCE

Telomere length is maintained in canine mammary gland tumors regardless of the age of the affected dog. Measurement of telomere length may be a useful tool for monitoring the in vivo effects of telomerase inhibitors in dogs with tumors.

Comparative genomic hybridization analysis of myoepithelial carcinoma of the breast

Although there seems to be a common stem cell for the two epithelial cell types in the breast, the vast majority of breast cancers exhibit a luminal phenotype. Pure myoepithelial carcinomas are rare. We report our findings of genetic alterations in these tumors. We have analyzed 10 cases of pure myoepithelial cell carcinomas using laser capture microdissection and comparative genomic hybridization. The mean number of changes was 2.1 (range 0-4), compared with a mean of 8.6 (range 3.6-13.8) in unselected ductal carcinomas. Common alterations included loss at 16q (3/10 cases), 17p (3/10), 11q (2/10), and 16p (2/10), regions also commonly deleted in ductal carcinomas. The single case in which both pure myoepithelial carcinoma and invasive ductal carcinoma was present showed 2 alterations in the myoepithelial tumor (losses at 17p and 17q), whereas the invasive ductal component showed 15 alterations (5 gains and 9 losses), including loss at 17p. The sharing of 17p loss in myoepithelial and ductal carcinoma is consistent with a common stem cell model in the breast. The relatively few genetic alterations in otherwise aggressive neoplasms suggests that myoepithelial tumors may be a good model for the delineation of genes important in breast tumorigenesis.

Expression of the c-kit protein is associated with certain subtypes of salivary gland carcinoma

The c-Kit protein, a receptor type tyrosine kinase that plays an important role in the development of hematopoietic cells, melanocytes, and germ cells, is expressed in mastocytosis, gastrointestinal stromal cell tumors (GISTs), germ cell tumors, and several other tumors. Gain-of-function mutations in exon 11 and exon 17 have been shown as a mechanism of c-kit activation in some tumors. To study the role of c-kit in salivary gland carcinomas, we analyzed the c-kit protein expression in 79 carcinomas of major and minor salivary glands by immunohistochemistry. Although varying in intensity of staining, c-kit expression was identified very often in adenoid cystic carcinomas (20/25), lymphoepithelioma-like carcinomas (6/6) and myoepithelial carcinomas (2/2), but not in other types of salivary gland carcinoma (0/46), P<0.00001. By DNA sequencing, genetic alteration of c-kit juxtamembrane domain (exon 11) and tyrosine kinase domain (exon 17) was not found in all the three types of salivary carcinoma that had c-kit protein expression. In conclusion, c-kit protein overexpression is involved in the pathogenesis of certain types of salivary gland carcinoma, but mutation of the gene is not the mechanism of c-kit activation.

Cytogenetic analysis of a primary salivary gland myoepithelioma

Myoepithelioma, a rare benign salivary gland neoplasm, is a tumor composed entirely of myoepithelial cells. Unlike pleomorphic adenoma, these tumors lack any ductal epithelial differentiation, and manifest a minor stromal element. Previous cytogenetic and molecular genetic studies have mainly investigated pleomorphic adenomas and reported recurring specific chromosomal alterations at 8q12 and 12q13-q15 regions. The cell origin of these alterations, however, remains speculative. We report the cytogenetic analysis of a parotid myoepithelioma and discuss the putative origin for the cells with cytogenetic alterations. Our analysis shows 12q12 involved in a translocation with a previously unreported partner (1q), and nonrandom del(9)(q22.1q22.3) and del(13)(q12q22). Our results indicate that the myoepithelial cell is the source of those cells with chromosomal alterations, and that myoepithelioma shares 12q alterations reported in a subset of pleomorphic adenomas.

[Expression of c-erbB-2 oncogene and mutation of p53 gene in myoepithelioma and myoepithelial carcinoma]

Expression of c-erbB-2 oncogene and mutant p53 protein were detected immunohistochemically in 14 cases of myoepithelioma and 6 cases of myoepithelial carcinoma of the salivary gland. Five of the 6 myoepithelial carcinomas and nine of the 14 myoepitheliomas were overexpression of c-erbB-2 oncoprotein. The salivary ductal epithelial cells near tumors were overexpression of c-erbB-2 oncoprotein. These results indicate that c-erbB-2 may be an initial oncogene during the histogenesis of myoepithelial tumors. The p53 protein was positive in five cases of the 6 myoepithelial carcinoma, whereas all myoepitheliomas were negative. The results indicate that the mutant p53 gene may play an important role in the carcinogenesis of myoepithelial carcinoma.

Quantitative multivariate analysis of myoepithelioma and myoepithelial carcinoma

The nuclear DNA content and morphologic data of 30 surgical samples (eight normal parotid gland, 12 myoepithelioma, and 10 myoepithelial carcinoma) were analyzed by the IBAS II analysis system. The results suggest that there are relationships between tumor ploidy distribution and prognosis, and that correct pathologic diagnosis can be obtained by the IBAS image system.