Malignant myoepithelioma (myoepithelial carcinoma) of the breast: an ultrastructural and immunocytochemical study

Adenomyoepithelioma of the Breast. A Case Report

Adenomyoepithelioma is a proliferative disorder of both epithelial and myoepithelial cells. This lesion may be found in salivary glands, skin appendages and, very rarely, in the mammary gland. Adenomyoepithelioma was first described in 1970 and very few cases have so far been reviewed in the literature. This paper reports the clinical, histological and immunohistochemical characteristics of an adenomyoepithelioma in a 24 year old woman; to our knowledge this is the first published case in such a young patient. The clinical feature suggested a fibroadenoma. A more complete study of the excised tumor tissue by immunohistochemical and ultrastructural analysis proved that the correct diagnosis was adenomyoepithelioma. Whether adenomyoepithelioma is a benign or a low-grade malignant lesion is still controversial and, therefore, the therapeutic approach is not well defined.

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.

Immunoreactivity for Sex Steroid Hormone Receptors in Pulmonary Hamartomas

Sex steroid hormone [ie, estrogen (ER), progesterone (PgR), and androgen (AR)] receptors have been identified previously in normal salivary glands and, more variably, in salivary gland and salivary gland-type tumors. No data are available, however, on their expression in pulmonary hamartoma, a benign biphasic tumor consisting of reactive epithelial cells and neoplastic fibromyxoid stroma, cartilage and fat, which shares some morphologic, immunophenotypic, and genotypic features to pleomorphic adenoma of major salivary glands. Thirty pulmonary hamartomas (15 in male patients and 15 in age-matched female patients), were evaluated for ER, PgR, and AR immunoreactivity, and also for mesenchymal, epithelial, and myoepithelial markers, in the fibromyxoid, epithelial, and chondroid components. ER immunoreactivity was encountered in 90% of hamartomas, PgRs in 90%, and ARs in 53% (P<0.001), but not in normal lung tissues. ARs were confined to males (P<0.001), with a marginal prevalence in the fibromyxoid component (P=0.067). PgRs and ERs were instead present in both sex, with the former being restricted to the fibromyxoid stromal component (P<0.001) and the latter preferentially located in epithelial cells (P=0.107). In most cases, fibromyxoid stroma and spindle cells surrounding the chondroid foci displayed simultaneous immunoreactivity for ERs, PgRs, and ARs, along with immunoreactivity for vimentin, S-100 protein, glial fibrillary acid protein, smooth muscle actin, and calponin but lack of staining for cytokeratins. This profile is consistent with an incomplete myoepithelial differentiation of the receptor-expressing mesenchymal cells. In conclusion, sex steroid hormone receptor expression is a nonrandom event in pulmonary hamartoma, and may be related to the development and growth of this tumor.

Metaplastic Sarcomatoid Carcinoma of the Breast With Absent or Minimal Overt Invasive Carcinomatous Component

Metaplastic carcinomas of the breast are a heterogeneous group of neoplasms ranging from tumors with a predominant component of overt carcinoma and focal mesenchymal differentiation to keratin-positive tumors with pure sarcomatoid morphology. We examined the clinicopathologic features of 22 patients previously diagnosed at M.D. Anderson Cancer Center with metaplastic carcinoma of the breast with pure or almost pure sarcomatoid morphology. Patients were included in the study if their tumors had sarcomatoid morphology and: 1) an invasive carcinomatous component identifiable on hematoxylin and eosin stains comprising less than 5% of the invasive tumor; or 2) associated ductal carcinoma in situ; or 3) immunohistochemical expression of keratin in the sarcomatoid areas. Patients with low-grade fibromatosis-like metaplastic tumors and those who received neoadjuvant chemotherapy were excluded. Axillary lymph node dissection or limited axillary node excision was performed in 17 patients, including 1 patient who had a sentinel lymph node biopsy. Lymph node involvement occurred in only 1 patient and consisted of a single 3.5-mm metastasis. Clinical follow-up was available for 21 patients and ranged from 4 months to 155 months (median follow-up, 35 months). Ten patients experienced local relapse, including 7 of 11 patients treated with breast-conserving surgery, and 9 developed distant metastases, most frequently to the lungs. These findings suggest that metaplastic sarcomatoid carcinomas that lack or have only a minimal overt invasive carcinomatous component have a biologic behavior similar to that of sarcomas. In addition to systemic treatment, early aggressive local therapy is recommended, as these patients have a high rate of local relapse.

The significance of focal myoepithelial cell layer disruptions in human breast tumor invasion: a paradigm shift from the "protease-centered" hypothesis

Human breast epithelium and the stroma are separated by a layer of myoepithelial (ME) cells and basement membrane, whose disruption is a prerequisite for tumor invasion. The dissolution of the basement membrane is traditionally attributed primarily to an over-production of proteolytic enzymes by the tumor or the surrounding stromal cells. The results from matrix metalloproteinase inhibitor clinical trials, however, suggest that this "protease-centered" hypothesis is inadequate to completely reflect the molecular mechanisms of tumor invasion. The causes and signs of ME cell layer disruption are currently under-explored. Our studies revealed that a subset of pre- and micro-invasive tumors contained focal disruptions in the ME cell layers. These disruptions were associated with immunohistochemical and genetic alterations in the overlying tumor cells, including the loss of estrogen receptor expression, a higher frequency of loss of heterozygosity, and a higher expression of cell cycle, angiogenesis, and invasion-related genes. Focal ME layer disruptions were also associated with a higher rate of epithelial proliferation and leukocyte infiltration. We propose the novel hypothesis that a localized death of ME cells and immunoreactions that accompany an external environmental insult or internal genetic alterations are triggering factors for ME layer disruptions, basement membrane degradation, and subsequent tumor progression and invasion.

Clinical presentation and long-term outcome of pure myoepithelial carcinoma of the breast

INTRODUCTION

Pure myoepithelial carcinoma of the breast is a rare tumour of controversial histogenesis. Little is known about its natural history and long-term outcome following treatment.

METHODS

All patients with pure myoepithelial carcinoma treated at our institution between 1970 and 2001 were studied with respect to pathological features, outcome and prognosis.

RESULTS

Six patients were identified. The median age was 60 (40-66) years and median follow-up was 34.5 months (range 14-76) months. Four tumours were T1 and one was T2 (one tumour size unknown). There were two moderately differentiated and three well-differentiated tumours (grade could not be assessed in one patient). Oestrogen and progesterone receptor could be assessed in five patients and all were negative. Primary treatment was wide local excision with clear radial margins. Lymph node assessment was negative in all patients. One patient received adjuvant radiotherapy. Three patients developed local recurrence at 15, 38 and 50 months and two patients developed distant metastasis at 30 and 79 months. The local recurrences were treated by further excision but two patients developed distant metastasis at intervals of 15 and 26 months, respectively. Two patients have died of the disease and four remain well. The 2-year and 5-year survival was 88% (SE, 6) and 55% (SE, 16), respectively. Large tumour size is a prognostic indicator of poor outcome.

CONCLUSION

Pure myoepithelial carcinoma of the breast adopts an aggressive clinical course with an outcome comparable to poorly differentiated adenocarcinoma of the breast.

[Breast myoepithelioma. Diagnostic and therapeutic difficulties. A case report]

Breast myoepithelioma is rare. The case of a 61-year-old female is reported here. The tumor was clinically, radiologically and macroscopically demarcated. Diagnosis was based on histological and immunohistochemical studies. At the time of diagnosis the tumor consisted of myoepithelial cells with few cellular atypias and a low mitotic activity. Tumor cells expressed vimentin, actin, S100 protein and cytokeratin. No local or distant metastases were found. The patient had been treated initially with a large excision of tumor. Local recurrences detected one year after initial surgery and showed a similar morphology and immunoreactivity with higher mitotic activity. Mastectomy with axillary dissection was performed. Neither recurrences nor distant metastases detected two years later. Myoepithelial tumors which are generally considered as benign or low-grade lesions can give rise to a wide range of clinical evolution.

An immunohistochemical study of metaplastic spindle cell carcinoma, phyllodes tumor and fibromatosis of the breast

The diagnosis of metaplastic (sarcomatoid) carcinoma (MSC) of breast often requires immunohistochemistry with a cytokeratin (CK) panel to distinguish them from phyllodes tumors (PT), primary sarcomas, and fibromatoses. CK staining may be heterogeneous in metaplastic carcinomas. The aim of the study was to investigate the theory that MSCs show evidence of myoepithelial differentiation and to evaluate immunohistochemical markers that may be helpful in distinguishing MSCs from PT and fibromatosis. We reviewed histology and performed immunohistochemistry for AE1/AE3, 34betaE12, CK5 and CK14, Cam5.2, CK7 and CK19, epithelial membrane antigen (EMA) (B55), smooth muscle actin (SMA), S100, desmin, vimentin, CD31, CD34, and bcl-2 on paraffin-embedded tissue from 18 MSCs, 26 PTs, and 8 fibromatoses. We assessed staining by using a semiquantitative method. Sarcomatous areas in MSCs were positive for 34betaE12 in 11 cases; for SMA in 10; for CK5 in 7; for CK14 in 6; for Cam5.2, AE1/AE3, and S100 in 5; and for CK7 and CK19 in 3. No CK expression was seen in stromal areas in PT or in fibromatoses. CD34 and bcl-2 were more frequently expressed in spindle cell areas in PTs (18 and 12 of 26, respectively) than in MSCs (0 and 2 of 18, respectively). MSCs show strong evidence of myoepithelial differentiation. CD34 and, to a lesser extent, bcl-2 positivity in PTs may be helpful in differentiating these two lesions from MSCs, particularly in small biopsies, because CK staining in MSCs may be heterogeneous. In our hands, 34betaE12 was the CK most frequently expressed in sarcomatoid areas in MSCs.

Salivary-type neoplasms of the breast and lung

Salivary-type tumors occur in multiple sites in the human body, likely related to a basic structural homology between exocrine glands in these different anatomic areas. This paper reviews these salivary gland tumor types in breast tissue and lung. Salivary-type tumors of both breast and lung are relatively uncommon in comparison to their salivary gland counterparts. This may be attributable in part to lack of familiarity with these tumors in extra-salivary sites, and in part to histologic overlap with other primary and metastatic tumor types. Recognition of these entities is improving as the clinical and pathologic features are better delineated, and tumors are more accurately classified. Prediction of malignant behavior is not always possible in these unusual sites. In some instances, such as adenoid cystic carcinoma, behavior is known to differ considerably from that of analogous primary salivary gland tumors and in other instances there are simply too few reported cases to allow for adequate prognostication. In fact, more recent papers discuss the need to consider a spectrum encompassing benign and malignant lesions, in both breast and lung. Of course, some entities show clear-cut evidence of malignancy with documented potential for metastasis, others show bland features and well-reported benign behavior, and the less well-defined entities reside between these two extremes. The molecular pathology of salivary gland tumors has been reasonably well investigated in that location; however; there are few molecular studies devoted to salivary-type tumors of the breast and lung. This represents a potential area for future growth in further clarifying these tumors and their behavior.

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.

Multifocal, nascent, and invasive myoepithelial carcinoma (malignant myoepithelioma) of the breast: an immunohistochemical and ultrastructural study

This report describes the light microscopic (LM), immunohistochemical (IHC), and electron microscopic (EM) features of a multifocal, nascent, and invasive myoepithelial carcinoma of the breast. By LM, the spindle cells disclosed fibrillar acidophilic cytoplasm, mild nuclear atypia, and a low mitotic index. Myoepithelial differentiation was established through IHC (single- and double-labeling techniques) and EM: periductal and infiltrating spindle cells coexpressed total muscle actin, alpha-smooth muscle actin, vimentin, cytokeratin 14, and pankeratin, and their EM features were characteristic of myoepithelial cells, i.e., perinuclear tonofilaments, subplasmalemmal bundles of microfilaments with dense bodies, intermediate junctions, poorly developed desmosomes, pinocytic vesicles, and fragmented external lamina. No invasive epithelial cells disclosed luminal differentiation (by LM, IHC, EM), identifying, thus, this neoplasm as a pure spindle cell myoepithelial carcinoma of the breast.

Rare case of biphasic tumor of the breast with prominent CD34-positive spindle cells

We report an unusual case of biphasic tumor of the breast with prominent CD34-positive spindle cells. A 53-year-old woman presented with a mass in her right breast. Following an incisional biopsy, a partial mastectomy was done. Histologically, the tumor was a biphasic variant of a malignant spindle cell tumor of the breast. The lack of a leaf-like structure, together with the apparent myoid features of the spindle-shaped tumor cells, made it difficult to distinguish from malignant phyllodes tumor and from myoepithelial carcinoma. Immunohistochemistry revealed the spindle-shaped tumor cells to be myofibroblastic, but not myoepithelial in nature, ultimately categorizing this tumor as a malignant phyllodes tumor with prominent myofibroblastic differentiation.

Cutaneous myoepithelioma: an under-recognized cutaneous neoplasm composed of myoepithelial cells

Benign and malignant neoplasms of myoepithelial cells comprise a rare but well-characterized group of tumors, among which myoepithelioma of the salivary glands is the best known. Extrasalivary examples of myoepithelioma also have been described in the breast, larynx, and retroperitoneum. Recently, myoepithelioma of the soft tissue also has been reported. According to this description, myoepithelioma and mixed tumors arising in the skin and subcutis represent points along a clinicopathologic spectrum of cutaneous and soft-tissue tumors. To the best of our knowledge, there has been only one case report of an entirely cutaneous myoepithelioma in the literature. We report herein five additional examples of purely myoepithelial tumors located exclusively in the dermis. Histopathologically, the neoplasms were well-circumscribed dermal lesions composed of fascicles of spindle cells with eosinophilic cytoplasm and ovoid-to spindle-shaped nuclei. Focally, neoplastic aggregations of more epithelioid cells representing large round cells with abundant pale cytoplasm arranged in solid clusters, cords, or strands were also seen. Ductal differentiation was not identified in either of these solid aggregations of epithelioid cells or in the fascicles of spindle-shaped cells. Nuclear pleomorphism in epithelioid and spindle-cell areas was mild, and mitotic figures were very sparse. In some cases, small, necrotic areas were seen within the solid aggregations of spindle-shaped cells. Neoplastic stroma was scant and composed of fibrillary collagen and abundant mucin. In one case, the stroma consisted of clusters of mature adipocytes intermingled with fascicles of myoepithelial cells. Areas of chondroid or osteoid metaplasia were not seen in any of the cases. Immunohistochemically, neoplastic cells expressed positivity for muscle specific actin (HHF35), alpha smooth muscle actin (IA4), S-100 protein, glial fibrillary acidic protein (GFAP), and epithelial membrane antigen (EMA), whereas stains for pan-cytokeratin (MNF116) were focal and weak. The findings in this report expand the clinical and histopathologic spectrum of cutaneous myoepithelioma, an under-recognized cutaneous neoplasm of myoepithelial cells.

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.

Malignant adenomyoepithelioma of the breast with malignant proliferation of epithelial and myoepithelial elements: a case report and review of the literature

Malignant adenomyoepithelioma of the breast is a rare lesion characterized by malignant proliferation of epithelial and myoepithelial cells that show characteristic histologic and immunohistochemical features. Eleven cases have been reported, 4 of which showed evidence of distant metastasis. The authors report a case of malignant adenomyoepithelioma in the axillary tail of a 71-year-old woman, one of the oldest patients described so far, and review the literature. Malignancy in the current case was evidenced by the presence of local invasion, high mitotic rate, and severe cytologic atypia. The tumor was associated with adenosis and lobular adenomyoepithelial hyperplasia. Malignant adenomyoepithelioma is a rare neoplasm, diagnosable by light microscopy and immunohistochemistry. To date, it has only been reported in women, who ranged in age from 26 to 76 years. Metastases have only been documented in tumors 2.0 cm in diameter or larger.

Benign myoepithelioma of the skin

A case of cutaneous myoepithelioma is reported. The tumor was composed of spindle-shaped, epithelioid, and plasmacytoid (hyaline) cells. It exhibited a widespread immunoreactivity for low molecular weight keratins and protein S-100, being irregularly positive for smooth muscle actin. Ultrastructural studies of tumor cells showed a variable content of intermediate filaments, with focal densities resembling smooth muscle dense bodies. A well-developed basal lamina, pinocytotic vesicles, and some desmosomes were also observed. In spite of being accepted as an individual entity, myoepitheliomas probably belong to a family of lesions that include mixed tumors. Therefore, this case can be considered as a salivary-gland-type tumor, probably originating from myoepithelial cells of sweat glands. The existence of this unique neoplasm provides further support to the debated role of myoepithelial cells in the development of mixed tumors.

Clear cell mammary malignant myoepithelioma with abundant glycogens

Malignant myoepithelioma (myoepithelial carcinoma) of the breast is extremely rare. A case is reported of a 46 year old female with clear cell mammary malignant myoepithelioma that, on histological examination, was glycogen abundant clear cell carcinoma. Immunohistochemically, the clear cells showed myoepithelial differentiation--that is, they were a smooth muscle actin and S100 protein positive. This case shows that glycogen abundant clear cell carcinoma is a variant of malignant myoepithelioma of the breast.

Pleomorphic adenoma of the breast: case report and review of the literature

A tumor of the right breast was noticed in a 70 year old female. The tumor was round, 1 x 1 cm, and was encapsulated with thin fibrous tissue. The boundary was clear. The cut surface showed a mosaic pattern of brown and white dots and the texture was gritty. Histologically, glandular structures, trabecular or solid epithelial cell nests, myxoid, cartilaginous and osteoid areas, and one ossifying focus were found. Round, polyhedral or fusiform myoepithelial cells proliferated around the glandular structures and were dispersing into the myxoid and cartilaginous tissue. Myoepithelial proliferation was especially marked around the small glandular structure. Immunohistochemically, S-100 protein was strongly positive for the myoepithelial cells around the glandular structures and in the cartilaginous tissue. Until now, 54 cases of pleomorphic adenoma of the breast have been reported. In those cases, the subareolar region was a common site for the tumor, and pleomorphic adenoma was thought to arise from large ducts in this region. No Oriental patients have been reported in the literature.

Malignant myoepithelioma (myoepithelial carcinoma) of the breast: a detailed cytokeratin study

AIMS

To study the expression of a range of cytokeratins by malignant myoepithelioma of the breast.

METHODS

Immunophenotyping was carried out using a panel of antibodies on paraffin wax embedded and frozen material using immunohistochemistry and double-labelled immunofluorescence. Electron microscopy was also performed.

RESULTS

The tumour cells were positive for CAM 5.2, actin, vimentin, and cytokeratin 14 and negative for cytokeratins 18 and 19. Electron microscopy showed well formed desmosomes and hemidesmosomes together with pinocytic vesicles, plentiful rough endoplasmic reticulum and 6 nM microfilaments with focal densities.

CONCLUSIONS

The pattern of cytokeratin expression provides further evidence that tumours with a specific myoepithelial phenotype occur rarely in the breast.

Intralobular growth of myoepithelial cell carcinoma of the breast

Two cases of intralobular carcinoma of the breast showing myoepithelial cell differentiation are reported. One was an in situ lesion localized within a fibroadenoma; the second was predominantly in situ, but areas of invasion were present. The neoplastic cells had round to ovoid nuclei and were polygonal to spindle in shape displaying glycogen rich clear cytoplasm. Alpha-smooth muscle actin was present in the cytoplasm of the neoplastic cells in both cases. In one case the same cells displayed cytoplasmic microfilaments at electron microscopic level. Intralobular growth of neoplastic myoepithelial cells has never been described in the literature, and this line of differentiation has to be added to the endocrine and apocrine features occasionally observed in in situ lobular carcinomas of the breast.

Myoepithelial carcinoma of the breast with distant metastasis and accompanied by adenomyoepitheliomas

A breast tumour in a 47-year-old female with axillary lymph node metastasis was interpreted as the rare malignant adenomyoepithelioma based on morphological and immunohistochemical studies. Multiple bone metastases developed and the patient died after 7 months. The malignant neoplasm consisted of cords and interlacing bundles of spindle cells with indistinct cell borders and clear cytoplasm. The cells stained positively for cytokeratin, S-100 protein, GFAP, and muscle-specific actin, and possessed basal lamina, pinocytic vesicles, tonofilaments, desmosomes, and intermediate filaments with dense bodies. In some areas, cells with microvillous projections enclosed small spaces. In the breast, foci of myoepithelioma with various morphological subtypes and infiltration coexisted, demonstrating the origin of the malignant tumour. The histogenesis of the myoepithelial tumours is discussed.

Benign and malignant neoplasms of myoepithelial cells: cytologic findings

We report two myoepithelial cell neoplasms; a salivary gland tumor was malignant and a breast neoplasm was benign. Both were studied histologically, immunohistochemically, cytologically, and ultrastructurally. The malignant myoepithelioma recurred twice and metastasized to one regional lymph node. This tumor was infiltrative with areas of necrosis and hemorrhage. It was composed of malignant-appearing spindle and plasmacytoid cells. Both types of cells were immunoreactive to muscle specific actin, S-100 protein, cytokeratin, vimentin, and neuron-specific enolase. Ultrastructurally, features of myoepithelial cells were seen. Fine-needle aspirate smears showed spindle and plasmacytoid cells, numerous mitoses, and malignant-appearing nuclei. Spindle-cell adenomyoepithelioma of the breast, a small well-circumscribed firm nodule, featured multiple lobules of spindle cells associated with clear-cell glands at the lobular periphery. Histologically and cytologically, the lesion was cellular but appeared benign. The differential diagnosis of myoepithelial neoplasms is discussed.

Epithelioid leiomyoma of the breast with granular cell change: a case report

A 42-year-old woman with an epithelioid granular cell leiomyoma of the right breast is reported. The cells were spindle to polygonal and displayed finely granular cytoplasm. The smooth muscle differentiation of this tumor was shown by the immunohistochemical positivity of the neoplastic cells with anti-alpha smooth actin and antidesmin antisera. Microfilaments with focal densities were present in the cytoplasm at an ultrastructural level. The granular cytoplasmic changes are related to a relevant number of lysosomes within the neoplastic cells.

Immunohistochemistry with keratin, vimentin, desmin, and alpha-smooth muscle actin monoclonal antibodies in canine mammary gland: benign mammary tumours and duct ectasias

Duct ectasias (n = 2) and different types of benign canine mammary tumours (n = 19) were studied immunohistochemically with monoclonal antibodies (MoAbs) directed against various human keratin types (K), alpha-smooth muscle actin, vimentin, and desmin. In the duct ectasias and in most tumours the epithelial structures revealed an inner and outer cell layer. The inner cell layer was characterized by labelling with K 7, 8, 18, 19 and mostly also with K 4 and/or K 10 MoAbs. The outer cell layer was almost invariably labelled by K 14, K 14 and 17, and a-smooth muscle actin MoAbs. The labelling patterns of both duct ectasias and tumours corresponded largely to the patterns observed in normal mammary gland tissue, although a more distinct heterogeneity was seen. Tumours histomorphologically assumed to be of a myoepithelial origin did not show immunohistochemical features of myoepithelial cells. The myoepithelial nature of the vast majority of spindle-shaped cells present in the adenomas of the complex type and in the fibroadenomas of the benign mixed type could not be confirmed immunohistochemically. These cells, however, unequivocally expressed vimentin, suggesting proliferation of stromal cells in these tumours, which in the fibroadenomas of the benign mixed type may show metaplasia to bone or cartilage. In the duct ectasias and in some tumours, a fraction of elongated stromal cells, probably representing myofibroblasts, was labelled with the alpha-smooth muscle actin MoAb.

Immunohistochemistry with keratin, vimentin, desmin, and alpha-smooth muscle actin monoclonal antibodies in canine mammary gland: malignant mammary tumours

Ten malignant canine mammary gland tumours and five metastases from three of these tumours were studied immunohistochemically with monoclonal antibodies (MoAbs) directed against different human keratin types (K), alpha-smooth muscle actin, vimentin, and desmin. In all tumours the neoplastic epithelium was rather homogeneously labelled with the keratin MoAbs RCK 102 (K 5 and 8) and CAM 5.2 (K 8). The adenocarcinomas (n = 5), the solid carcinomas (n = 2), and the carcinosarcoma (n = 1) showed heterogeneous labelling with the MoAbs specific for luminal cell antigens in the normal canine mammary gland, i.e., K 18, K 7 and K 19 MoAbs. These cells were also immunoreactive with K 4 and K 10 MoAbs. The spindle cell carcinomas (n = 2), however, did not react with these MoAbs. All tumours except one adenocarcinoma were characterized by the absence of immunoreactive labelling with the alpha-smooth muscle actin MoAb. In the solid carcinomas this was associated with the absence of labelling with one or both basal cell specific keratin MoAbs, i.e., 8.7 (K 14 and 17) and RCK 107 (K 14), respectively. In contrast, the other malignant tumours showed marked labelling of neoplastic epithelium with these MoAbs. Another remarkable finding was the labelling of a limited to moderate number of neoplastic epithelial cells with the vimentin MoAb. The presence of such labelling patterns in canine mammary gland tumours may be indicative of malignancy. Metastatic tumour tissues had a labelling pattern largely similar to that of the primary tumour, although also loss of reactivity for some keratin MoAbs was seen.

Adenomyoepithelioma (myoepithelioma) of the breast in a male

Adenomyoepithelioma (myoepithelioma) of the breast in a 47-year-old man is reported. The tumor consisted of a prominent proliferation of spindle cells surrounding mammary ducts. Immunohistochemical and electron microscopic observations confirmed the myoepithelial origin of these spindle cells. This is the first report of an adenomyoepithelioma of the breast that developed in a male.

Adenomyoepithelioma of the breast: fine-needle sampling with histologic, immunohistologic, and electron microscopic analysis

Fine-needle sampling was performed in a woman with a subareolar breast mass. The cytologic diagnosis was consistent with a benign sweat gland-type tumor. Cytologic features included epithelial cells and spindle-shaped cells lying free or in fibrillary myxoid ground substance. Histologic study revealed the biphasic appearance of this tumor composed of proliferating myoepithelial cells and glandular epithelial cells as supported by immunohistologic and electron microscopic analyses. Epithelial cells were strongly positive for cytokeratins, and spindle cells were positive for actin, S-100 protein, and keratin and showed ultrastructurally typical features of myoepithelial cells.

Myogenic stromal tumor of the male breast (so-called myofibroblastoma)

A case of a distinctive stromal tumor of the male breast, recently designated as myofibroblastoma, is reported. A fascicular clustering of spindle cells with intervening hyaline bands was the dominant pattern, but areas of myxoid transformation were present. Ultrastructure revealed a large predominance of fibroblastlike cells, often containing dispersed or aggregated intermediate and/or thin filaments. These cells depicted numerous thin processes encircling collagenous bundles. Primitive mesenchymal and typical smooth muscle cells were present, but myofibroblasts were not identified. Vimentin was diffusely expressed, whereas desmin and muscle-specific actin were detected in, respectively, 50% to 60% and 15% to 25% of the cell population. The designation of myogenic stromal tumor is, therefore, considered more appropriate.

Myoepitheliomas in inbred laboratory mice

Myoepitheliomas are subcutaneous tumors that arise from myoepithelial cells of various exocrine glands. In a retrospective study of 142 tumors observed over a period of 3 years, myoepitheliomas occurred spontaneously in A/HeJ, A/J, BALB/cJ, BALB/cByJ, LLC.A/Ckc, and NOD/Lt inbred strains of mice. Tumors presented primarily in the subcutaneous tissues of the ventral neck (74% of the myoepitheliomas evaluated) but were observed in several other subcutaneous locations, including the head, perineum, and ventral abdomen. These areas were adjacent to salivary, mammary, clitoral, preputial, and Harderian glands. Forty myoepitheliomas were tested by the avidin-biotin complex technique with a panel of antisera specific for mouse keratins, intermediate filaments, and other cytoskeletal proteins to determine the cell type from which this neoplasm originated. Antibodies directed against the specific mouse keratins K5, K6, and K14, and a broadly cross-reactive cytokeratin antibody stained acinar and ductal myoepithelial cells in normal mammary, salivary, and Harderian glands, and neoplastic cells in all cases. Antisera directed against a smooth muscle actin (anti-alpha-sm-1) stained acinar myoepithelial cells of the glands and vascular smooth muscle but neither ductular myoepithelial cells nor tumor cells. This supports the notion that these tumors originate from extraglandular ductular myoepithelial cells. Southern blots, prepared from DNA extracted from nine myoepitheliomas, did not show restriction fragment length polymorphisms when mouse mammary tumor virus (MMTV) cDNA or Int-1 genomic DNA probes were used; this implies that a retrovirus is not the etiologic agent.

Malignant myoepithelioma of the larynx with massive metastatic spread to the liver: an ultrastructural and immunocytochemical study

A malignant myoepithelioma arising in the submucosal glands of the larynx of a 71-year-old man is reported. The patient presented with a neck mass and massive metastatic involvement of the liver. Light microscopy of a liver biopsy specimen and fine-needle aspiration sample of the neck mass revealed a poorly differentiated carcinoma. Electron microscopic study of a second liver biopsy specimen demonstrated unequivocal features of myoepithelial differentiation; this was further confirmed by the strong cytokeratin and S-100 protein positivity and carcinoembryonic antigen negativity of the tumor cells. Myoepitheliomas are rare tumors, and most reported cases have been benign or of low-grade malignancy. The present case is unique because of its mode of presentation and fulminant course. It also underscores the usefulness of electron microscopy as a diagnostic modality in the work-up of metastatic lesions.

An epithelial and spindle cell breast tumour of myoepithelial origin. An immunohistochemical and ultrastructural study

An infiltrating epithelial and spindle cell neoplasm developed in the breast of a 63-year-old female. An excisional biopsy was performed. Recurrence with rapid growth due to cyst development eventually resulted in more radical surgery. Interim fine needle aspirations had established its partially cystic nature. The unique microscopic appearance prompted the application of immunohistochemistry and electron microscopy. The tumour cells were found to exhibit characteristics denoting squamous and myoepithelial differentiation. Histopathological features of malignancy were absent. Our findings demonstrate the differentiation potential of breast epithelium. They are in concordance with the results of previous studies which delineate the histochemical and ultrastructural features of myoepithelial and establish the relationship of these cells to squamous metaplasia.

Myoepithelioma--new concepts of histology and classification: a light and electron microscopic study

Based on histological, immunohistochemical, and ultrastructural studies, it is now apparent that the modified myoepithelial cell component of pleomorphic adenomas has a considerable range of cytological features. We reasoned that myoepitheliomas could be tumors with a similar spectrum of neoplastic myoepithelium but lacking the ductal element displayed in pleomorphic adenomas. A review of available salivary gland tumors identified 40 examples based on this definition. Architecturally, these myoepitheliomas displayed either nonmyxoid (solid), myxoid (pleomorphic adenoma-like), reticular (canalicularlike), or mixed growth patterns, while cytologically the lesions were composed of spindle-type (32.5%), hyaline-type (7.5%), epithelial-type (45.0%), clear-type (2.5%), or mixed-type (12.5%) tumor cells. Electron microscopy was carried out on eight examples and detailed immunohistochemistry on two methanol-fixed cases. As a result of the current review of myoepitheliomas and the description of similar lesions in the literature, it is our contention that salivary gland myoepitheliomas are not as rare as has been purported.

Spindle-cell adenomyoepithelioma of the breast. A microscopic, ultrastructural, and immunocytochemical study

Two patients developed nodular, well-circumscribed tumors of the breast, discovered by mammography. They were fibroadenoma-like by gross examination and biphasic by light microscopy, containing both tubular glands and spindled myoid cells. Immunocytochemical studies revealed cytokeratin and S-100 immunoreactivity in both the spindled myoid cells and in the tubuloglandular cells (S-100 was focal in the latter). In addition, the spindled myoid cells were immunoreactive for vimentin but negative for desmin. Ultrastructural studies showed the tubular glands to be composed of luminal epithelial cells focally surrounded by myoepithelial cells, but the stroma contained spindled myoepithelial cells admixed with occasional fibroblasts. The diagnostic term, "adenomyoepithelioma," is appropriate for biphasic tumors having both glandular and myoepitheliomatous differentiation. Although additional experience is necessary to be conclusive regarding the biologic behavior of these unusual lesions, the authors believe the adenomyoepitheliomas described here are benign. They were well circumscribed without invasion of adjacent breast, contained neither mitotic figures nor cytologic atypia, and have not recurred or metastasized (6 and 10 months after removal).

Clear cell myoepithelial neoplasm of the breast

Primary clear cell tumors of the breast are rare neoplasms. Traditionally, their differential diagnosis has included lipid-rich, glycogen-rich, and secretory carcinomas of the breast. Although clear cell myoepithelial tumors of the salivary gland and skin have been reported, a primary clear cell myoepithelial carcinoma of the breast has not been previously described. We report a case of clear cell myoepithelial neoplasm of the breast showing an infiltrative histologic growth pattern highly suggestive of carcinoma. Electron microscopy showed evidence of myoepithelial differentiation manifested by cytoplasmic microfilaments with randomly dispersed fusiform densities in conjunction with specialized membrane junctions and remnants of basal membrane. Immunohistologically, the tumor cells were positive for actin, keratin, and S-100 protein. This tumor should be included in the differential diagnosis of the clear cell neoplasms of the breast.

Adenomyoepithelioma of the breast

Adenomyoepithelioma, an uncommon benign breast tumor in which the proliferation of myoepithelial cells is a conspicuous component, was examined in 18 women. The initial clinical finding was usually a mass in the periphery of the breast. Grossly, adenomyoepithelioma produced a circumscribed, firm tumor (average, 1.5 cm) with nodularity and cysts noted in some instances. Proliferating myoepithelial cells and gland-forming epithelial cells were conspicuous in all cases. In most, myoepithelial cells were polygonal and had clear vacuolated cytoplasm. Myoid, spindle-cell differentiation was rarely prominent, but cells of this type were present focally in most cases. Intraductal papillary adenomyoepitheliomatous hyperplasia was present within the tumors and sometimes in surrounding ducts. Immunohistochemical studies distinguished epithelial from myoepithelial cells. Hormone receptor studies showed four tumors were estrogen receptor positive, two were estrogen receptor negative, and five were progesterone receptor negative. One patient who underwent immediate mastectomy is well 4 years later. Two of the 17 women treated by local excision had recurrent adenomyoepithelioma in the same breast. All 18 patients remain well from 0.5 to 5.5 years after diagnosis. No patient had prior, coexistent, or subsequent adenocarcinoma of either breast. These findings indicate that adenomyoepithelioma is a benign tumor that can be adequately treated by complete local excision.

Aspiration biopsy cytology of mammary myoepithelioma

A case of ultrastructurally confirmed myoepithelioma of the breast studied by fine-needle aspiration biopsy is reported. Aspirated tumor cells were spindle-shaped with well-defined cytoplasm and oval nuclei showing no remarkable nuclear pleomorphism. They were seen mainly in irregular bundles with strong cellular cohesiveness. Their cytoplasm contained S-100 protein demonstrated by the peroxidase antiperoxidase staining technique.