Myoepithelioma: definitions and diagnostic criteria

Adhesion and protease activity in cell lines from human salivary gland tumors are regulated by the laminin-derived peptide AG73, syndecan-1 and beta1 integrin

We studied the induction of protease activity by the laminin alpha1-derived peptide AG73 in cells from adenoid cystic carcinoma (CAC2) and myoepithelioma (M1), respectively a malignant and a benign salivary gland tumors. Laminin alpha1 chain and MMP9 were immunolocalized in adenoid cystic carcinoma and myoepithelioma in vivo and in vitro. Cells grown inside AG73-enriched laminin-111 exhibited large spaces in the extracellular matrix, suggestive of remodeling. The broad spectrum MMP inhibitor GM6001 decreased spaces induced by AG73 in CAC2 and M1 cells. This result strongly suggests that AG73-mediated matrix remodeling involves matrix metalloproteinases. CAC2 and M1 cells cultured on AG73 showed a dose-dependent increase of MMP9 secretion, as detected by zymography. Furthermore, siRNA silencing of MMP9 decreased remodeling in 3D cultures. We searched for AG73 receptors regulating MMP9 activity in our cell lines. CAC2 and M1 cells grown on AG73 exhibited colocalization of syndecan-1 and beta1 integrin. siRNA knockdown of syndecan-1 expression in these cells resulted in decreased adhesion to AG73 and reduced protease and remodeling activity. We investigated syndecan-1 co-receptors in both cell lines. Silencing beta1 integrin inhibited adhesion to AG73, matrix remodeling and protease activity. Double-knockdown experiments were carried out to further explore syndecan-1 and beta1 integrin cooperation. CAC2 cells transfected with both syndecan-1 and beta1 integrin siRNA oligos showed significant decrease in adhesion to AG73. Simultaneous silencing of receptors also induced a decrease in protease activity. Our results suggest that syndecan-1 and beta1 integrin signaling downstream of AG73 regulate adhesion and MMP production by CAC2 and M1 cells.

Epithelial-myoepithelial parotid carcinoma after kidney transplantation

The occurrence of a second malignant neoplasm (SMN) in patients who have been submitted to kidney transplantation is increasing and causes concern; parotid carcinoma is rarely reported after transplantation and may be related to long-term chemotherapy.Salivary gland carcinomas displaying exclusively myoepithelial differentiation-myoepithelial carcinomas (EMC) are rare, being less than 1% of all salivary gland tumours. EMC arises most commonly in the parotid gland and usually occurs in women. Their histopathologic features, immunohistochemical profile and clinical behaviour remain controversial.

Malignant myoepithelial tumor of soft tissue: a report of two cases of the lower extremity and a review of the literature

Myoepithelial tumors of the soft tissues have only recently been described. Two cases of lower extremity malignant myoepithelial tumors are reported. One case of malignant mixed tumor overlying the gastrocnemius muscle was treated with wide local excision, but metastasized to regional lymph nodes 14 months after surgical excision. One patient with malignant myoepithelioma of the right lower leg was treated with limb amputation and is alive without disease at 46 months. A review of the literature discloses 120 additional cases of soft tissue myoepithelial tumors, 102 of which are myoepitheliomas and 18 are mixed tumors. Thirty-seven percent of the myoepitheliomas met the criteria for malignancy, and 33% of the mixed tumors were malignant. Of these, 30% had locally recurrent disease and 32% developed metastatic disease. Treatment benefit from chemotherapy and radiation therapy is unclear.

Malignant Myoepithelioma of Cranial Dura

Malignant tumors of myoepithelial origin have been increasingly recognized at a variety of sites. Herein, we describe an example of malignant myoepithelioma arising in intracranial dura. The patient is a 47-year-old woman who presented with intracranial hemorrhage and on magnetic resonance imaging was found to have an enhancing tumor. No extracranial primary tumor was identified. A gross total resection was performed. Histologically, it varied in pattern from diffuse to focally (<10%) ductular and consisted of epitheloid to spindle cells showing marked mitotic activity. Prominent infiltration of the dura was noted. Immunohistochemical stains showed convincing expression of cytokeratins (AE1/AE3 and CAM 5.2), S-100 protein, smooth muscle actin, and glial fibrillary acidic protein. Electron microscopy performed on formalin-fixed, paraffin-embedded tissue demonstrated cohesive cells with focal intermediate filament content and surface basal lamina formation at stromal interfaces. Occasional desmosomes with tonofilaments surrounded intercellular lumina containing masses of filamentous material. This example of malignant myoepithelioma is the first convincing primary salivary gland type tumor to arise in an intracranial location outside the sellar region or ear. Intracranial dura should be added to various sites at which this morphologically heterogenous tumor may arise.

Plasmacytoid myoepithelioma of the palate in a child

BACKGROUND

Myoepithelioma is a rare benign salivary gland tumour, localized most frequently in the parotid and in minor intraoral salivary glands. There have been only four cases of myoepithelioma in children and adolescents reported in the English-language literature, all of them involving the plasmacytoid variant.

CASE REPORT

A 13-year-old boy, complained of a painless nodule of the palate. Incisional biopsy was performed and revealed large plasmacytoid cells with a round and eccentric nuclei. The diagnosis was consistent with myoepithelioma, plasmocytoid variant. Tumour cells were positive for cytokeratins, vimentin and S-100 protein. Surgical resection was performed and no evidences of tumour recurrence were observed after 6 years of the treatment.

CONCLUSION

Myoepithelioma is a very rare tumour in children and apparently presents a good prognosis, similar to occur in adult patients.

Mioepitelioma de glândula salivar menor: uma análise imunohistoquímica de quatro casos

INTRODUÇÃO E METODOLOGIA: Realizou-se um estudo imunohistoquímico em 4 casos de mioepiteliomas, visando traçar seu perfil quanto ao grau de diferenciação das células através dos anticorpos alfa-SMA, CK 14 e vimentina, bem como investigar o índice de proliferação celular pelo anti-PCNA, além de comparamos a imunorreatividade com o tecido glandular normal adjacente ao tumor. RESULTADOS: No tecido glandular normal as células mioepiteliais exibiram marcação para alfa-SMA e CK 14, enquanto que nas células ductais somente a presença da CK 14 foi verificada. Em todos os casos foi verificada positividade para CK 14 e vimentina, porém a CK 14 esteve presente somente em células epitelióides e fusiformes, enquanto que a vimentina mostrou-se positiva também nas células plasmocitóides. A alfa-SMA não foi detectada nas células neoplásicas. Imunopositividade para o PCNA foi observada em mais de 75% do componente celular dos tumores analisados, independente do tipo. CONCLUSÕES: Concluiu-se que não houve diferença na atividade proliferativa entre os tipos celulares presentes nos mioepiteliomas e, ainda, que os resultados deste estudo sugerem que as células constituintes desta neoplasia realmente representam células da linhagem mioepitelial, mas em diferentes estágios de diferenciação.

Myoepithelioma of minor salivary gland - An immunohistochemical analysis of four cases

Introduction and Methods

We performed an immunohistochemical study in four cases of myopitheliomas with objective to realize a profile in respect of differentiation grade by the monoclonal antibodies CK14, vimentin and alph-SMA, besides to investigate the cell proliferation by anti-PCNA, besides, we compare the immunoreactive with glandular normal tissue.

Results

In the glandular normal tissue the myoepithelials cells had shown expression for alpha-SMA and CK 14, while that in the ductals cells, only the presence of CK 14 was verified. All the cases was verified positivy for CK 14 and vimentin, however, CK 14 had been present only in epithelioid and fusiform cells, while that the vimentin revealed positive also in the cytoplasm of the plasmocytoid cells. alpha-SMA was not detected in the neoplasic cells. Immunopositivity for the PCNA was observed in more than 75% of the cellular component of the analyzed tumors, independent of the cellular type.

Conclusions

We concluded that it did not have difference in the proliferative activity among the cellular types presents in the myoepitheliomas and, still, the results of this study suggest that the constituent cells of this neoplasia one really represent cells of the mioepitelial ancestry, but in different stages of differentiation.

Application of Two Different Clones of Vimentin to the Diagnosis of Salivary Gland Tumors

With the evolution of IHC techniques, a broad range of antibodies have become available to diagnostic immunohistology. The authors observed different expressions of vimentin in salivary gland tumors using two clones of this antibody. This study was undertaken to show these differences comparing the immunoexpression of two clones of vimentin (V9 and Vim 3B4, DAKO, Carpenteria, CA) using 10 pleomorphic adenomas, 10 adenoid cystic carcinomas, and 4 epithelial/myoepithelial carcinomas of the salivary glands. The V9 clone of vimentin was much more efficient in demonstrating the myoepithelial cells in the different tumors studied. The Vim 3B4 clone was capable of detecting some myoepithelial cells, the plasmacytoid or modified myoepithelial cells in the pleomorphic adenoma, but was very weak in epithelial/-myoepithelial carcinomas. The difference between the two clones studied is a warning that pathologists need to know the specificity and sensitivity of the reagent they are using.

Myoepithelioma of the tongue

Soft tissue myoepitheliomas, in contrast to salivary gland myoepitheliomas, are benign neoplasms that typically occur in the soft tissues of the extremities. Both are characterized by a multilobular proliferation of polygonal to fusiform cells embedded in a variably myxoid to chondromyxoid matrix. A histologically similar lesion that has a marked predilection for the anterior dorsum of the tongue has been referred to as ectomesenchymal chondromyxoid tumor. The morphological and immunohistochemical resemblance of soft tissue myoepitheliomas to ectomesenchymal chondromyxoid tumors has led to the use of these designations interchangeably. We present a case of myoepithelioma of the tongue and review the literature, with emphasis on the differential diagnosis and histogenesis of this lesion and pertinent nosologic considerations.

Adenomyoepithelioma

Adenomyoepithelioma, strictly defined, is a proliferation of both epithelial and myoepithelial elements. The broad range of lesions that may fall under this umbrella, however, may be quite diverse. The diagnostic confusion surrounding this entity and its prognostic implications have led to a diagnosis by default as malignant and to overtreatment of some patients. We evaluated available material from a series of 35 women whose slides were seen in consultation and who were diagnosed with adenomyoepithelioma or a closely related lesion. This comprehensive review of the varied histology of adenomyoepithelioma and similar lesions and their immunohistochemical properties will assist general pathologists in evaluating these sometimes difficult lesions. Follow-up and treatment information demonstrates their benignity. Architecture and histologic features should be combined with immunohistochemistry when determining categorization.

Myoepithelioma of parotid gland presenting as infra-auricular subcutaneous mass

Myoepithelioma is a rare but well-characterized group of tumours, among which myoepithelioma of the salivary glands is the best known. We report two patients with myoepithelioma of parotid gland presenting as infra-auricular subcutaneous mass. The lesions were clinically suspected to be epidermal cyst. The biopsies revealed that most of the tumour cells showed epithelioid features with oval or spindle eosinophilic cytoplasm. No ductal or syringomatous epithelial structures were observed. The tumour cells showed cytoplasmic immunoexpressions of vimentin, cytokeratin (AE1/AE3), S-100 protein and smooth muscle actin (SMA). In one patient, a strong calponin positivity was observed. Maguetic resonance imaging (MRI) of both patients revealed exophytic, well-defined, strongly enhancing mass in superficial lobe of parotid gland, confirming the parotid gland origin. Myoepithelioma of parotid gland can be presented as a slowly growing tumour of pre- or infra-auricular area. In dermatologic department, it can be misdiagnosed as various dermal or subcutaneous tumours.

Myoepithelial cell-rich neoplasms: cytologic features of benign and malignant lesions

BACKGROUND

Lesions that contain abundant myoepithelial cells may present as a diagnostic challenge in fine-needle aspiration (FNA) specimens. Potential diagnostic problems may arise due to morphologic heterogeneity of myoepithelial cell-rich lesions and difficulty in predicting malignancy in FNA specimens. An accurate diagnosis is important, because malignant myoepithelial cell-rich lesions require a wider local excision and lymph node dissection. The authors characterized the cytologic features of myoepithelial cell-rich lesions in an attempt to define the criteria that facilitate distinction between benign and malignant tumors.

METHODS

FNA biopsies of myoepithelial cell-rich lesions with corresponding histologic specimens were selected. The cytology specimens were evaluated for the following criteria: cellularity, cell morphology, pleomorphism, chromatin pattern, presence of nucleoli, background material, necrotic debris, and presence of mitotic figures. A review of the histologic sections was performed for diagnostic confirmation.

RESULTS

Seventeen specimens from 17 different patients were selected. The histologic diagnoses were myoepithelial carcinoma (n = 6 patients), malignant mixed tumor with predominant myoepithelial carcinoma (n = 2 patients), epithelial-myoepithelial carcinoma (n = 1 patient), and benign mixed tumor (n = 8 patients). The primary sites included the parotid gland (n = 10 patients), submandibular gland (n = 3 patients), minor salivary gland (n = 3 patients), and breast (n = 1 patient). Most specimens, whether they were benign or malignant, were very cellular. Pleomorphism, coarse chromatin, prominent nucleoli, mitotic figures, and necrosis were observed only in malignant specimens. Background material and ductal cells were seen in both benign and malignant specimens.

CONCLUSIONS

The presence of pleomorphism, coarse chromatin, prominent nucleoli, mitotic figures, and/or necrosis should raise the possibility of myoepithelial carcinoma in FNA specimens from myoepithelial cell-rich lesions.

[Mixed tumor or myoepithelioma of the skin? Histologic and immunohistochemical features]

Mixed tumor, first reported in the parotid gland, is formed from the proliferation of epithelial and myoepithelial cells in a mesenchymatous stroma. We report the case of a woman hospitalized for a subcutaneous nodule of the thigh, characterized by a fast increased in size in 8 months. Microscopic analysis showed a proliferation of grouped and isolated spindle cells, without atypia or mitotic features. Few tubular features were noted. Stroma was hyalinized or myxoid. Neoplastic cells displayed immunohistochemical positivity with smooth muscle actin, keratin and S-100 protein. This neoplasm appeared mesenchymatous. The diagnosis was mixed tumor with a predominant myoepithelial component. This case underlines the difficulties encountered in defining this neoplasm. Some authors consider that myoepithelioma is a monophasic variant of mixed tumor; others consider that myoepithelioma is different from mixed tumor because its is more aggressive prognosis. The evolution of our case suggests that a myoepithelial differentiation should be a ma of poor prognosis.

The effect of laminin and its peptide SIKVAV on a human salivary gland myoepithelioma cell line

We have demonstrated that the basement membrane regulates the myoepithelioma. We are now studying the effect of laminin, a basement membrane protein, in the morphology of a cell line (M1) derived from human salivary gland plasmacytoid myoepithelioma. These cells were grown inside a three-dimensional preparation of laminin-1. Phenotype differences were assessed by light and transmission electron microscopy. In addition, we analysed the effect of a molecular domain of laminin-1, the peptide SIKVAV, on M1 cells. This peptide was chosen because it is effective in cell proliferation and differentiation. M1 cells grown inside laminin-1 were mostly plasmacytoid-like, while cells treated by SIKVAV showed light and electron microscopic features of typical plasmacytoid cells. This peptide also modulated smooth-muscle actin expression in M1 cells. We demonstrated that laminin-1 and its derived peptide SIKVAV morphoregulates myoepithelioma cells in culture.

Defining the role of myoepithelium in salivary gland neoplasia

Neoplastic myoepithelium is considered to be the key cellular participant in morphogenetic processes responsible for the variable histologic appearances of many salivary gland tumors. Nevertheless, controversy still exists concerning its participation in some types of salivary gland neoplasms. This has been largely due to the difficulty in fully characterizing the wide spectrum of morphologic and immunophenotypic expressions of neoplastic myoepithelium compared with the normal counterpart. However, in recent years, our understanding regarding the phenotypic, immunophenotypic, ultrastructural, and biochemical properties of myoepithelium has advanced. Here we discuss the role of neoplastic myoepithelium in the scope of salivary gland neoplasia and present this information from a practical diagnostic standpoint.

Cutaneous myoepithelioma: a clinicopathologic and immunohistochemical study of 14 cases

Analogous to mixed tumors of salivary glands (" pleomorphic adenomas" ), cutaneous mixed tumors (" chondroid syringomas" ) contain a ductal (epithelial) component and a variably prominent myoepithelial component. Tumors showing purely myoepithelial differentiation (myoepitheliomas) have only recently been recognized to arise in the dermis, and to date very few cases have been described. To characterize these tumors further, 14 cutaneous myoepithelial tumors were retrieved from the authors' consult files. Eleven patients were male and 3 were female; their median age was 22.5 years (range, 10 to 63 years), and 7 patients were between 10 and 20 years old. Tumor size ranged from 0.5 to 2.5 cm (mean, 1.1 cm). Most tumors arose on the extremities: 6 on the upper limbs, 6 on the lower limbs, and 1 each on the back and nose. Ten tumors were limited to the dermis, and 5 also extended into superficial subcutis. Thirteen tumors were myoepitheliomas (lacking ductal differentiation), and 1 tumor was a myoepithelial carcinoma (exhibiting severe cytological atypia and a high mitotic rate). Histologically, 7 tumors were solid, composed of ovoid to spindled, histiocytoid, or epithelioid cells with no significant stroma, and 7 were predominantly lobulated, with cords or nests of epithelioid, plasmacytoid, or spindled cells with a variably reticular architecture and a chondromyxoid or collagenous/hyalinized stroma. One tumor was composed solely of plasmacytoid (hyaline) cells, and 1 exhibited extensive adipocytic differentiation. Among the 13 myoepitheliomas, mitoses ranged from 0 to 6 per 10 high-power fields (HPFs) (mean, 1.5); 8 tumors contained no mitoses. The myoepithelial carcinoma had 39 mitoses per 10 HPFs. By immunohistochemistry, all cases were reactive for epithelial markers (keratins and/or epithelial membrane antigen [EMA]); 13 of 14 (93%) expressed S-100 protein, 10 of 11 expressed (91%) calponin, 11 of 14 (79%) expressed EMA, 9 of 14 (64%) expressed keratins, 8 of 14 (57%) expressed smooth muscle actin, 7 of 14 (50%) expressed glial fibrillary acidic protein, 3 of 11 (27%) expressed p63, and 1 of 6 (17%) expressed desmin. All 5 cases without keratin staining were diffusely positive for EMA, and all of these cases showed a solid growth pattern. Follow-up was available for 8 patients (median follow-up, 40 months; range, 6 months to 9 years); 3 tumors (38%) recurred locally, and 1 tumor (13%) also metastasized to the lymph nodes. The case that resulted in recurrence and metastasis had the highest mitotic rate (6 per 10 HPFs) of the cytologically benign tumors. Follow-up information was not available for the myoepithelial carcinoma. This study suggests that approximately 50% of cutaneous myoepitheliomas are distinctive lesions composed of a solid proliferation of cells with abundant eosinophilic syncytial cytoplasm, which often lack immunostaining for keratin, whereas the remainder demonstrate focally reticular architecture and myxoid stroma or plasmacytoid cells, similar to their counterparts in salivary gland and soft tissue. Whereas most cutaneous myoepitheliomas behave in a benign fashion, there is apparently a significant risk for local recurrence but a low metastatic potential.

Myoepithelioma of the soft tissue of the head and neck: a case report and review of the literature

BACKGROUND

Extraglandular myoepitheliomas are neoplasms that seldom occur in the soft tissue of the head and neck region. Misdiagnosis of these neoplasms as more aggressive tumors can lead to unnecessary treatment.

METHODS

We describe a myoepithelioma of cervical soft tissue. The histopathology of the tumor, its immunophenotype, its differential diagnosis, and a review of the literature are presented.

RESULTS

Histopathologically, the tumor was composed of epithelioid cells with eosinophilic cytoplasm and eccentric nuclei arranged in cords and files. On immunohistochemical analysis, the cells expressed cytokeratin 14, calponin, glial fibrillary acid protein, and p63 and showed focal positivity for S-100 protein. Together, these markers identified the cells as myoepithelial type. A literature review identified only five cases of myoepithelioma in the soft tissue of the head and neck region in which detailed clinical information was provided.

CONCLUSIONS

Myoepitheliomas can have cells with variable morphology arranged in different histologic patterns. Immunohistochemical analysis is crucial for unequivocal diagnosis when myoepitheliomas occur in extraglandular locations.

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.

Myoepithelial tumors of soft tissue: a clinicopathologic and immunohistochemical study of 101 cases with evaluation of prognostic parameters

Myoepitheliomas and mixed tumors were only recently recognized to occur primarily in soft tissue, and only small case numbers have been described. To characterize these tumors further and to evaluate prognostic parameters, 101 myoepithelial tumors of soft tissue were retrieved from the authors' consult files. Hematoxylin and eosin sections were reexamined, immunohistochemistry was performed, and clinical details were obtained from referring physicians. Fifty-three patients were male and 48 female (mean age 38 years; range 3-83 years). Tumor size ranged from 0.7 to 20 cm (mean 4.7 cm). Most tumors arose in the extremities and limb girdles: 41 in the lower limbs, 35 in the upper limbs, 15 in the head and neck, and 10 in the trunk. Fifty-four tumors were situated in subcutis and 37 in deep soft tissue (depth unstated in 10). Most cases were grossly well circumscribed; 43 showed microscopically infiltrative margins. Histologically, most tumors were lobulated, composed of cords or nests of epithelioid, ovoid, or spindled cells with a variably reticular architecture and a chondromyxoid or collagenous/hyalinized stroma. Eight cases showed a predominantly solid proliferation of spindled or plasmacytoid cells; 17 demonstrated ductular differentiation (mixed tumors). Cartilage was present in 6 cases, 6 contained bone, and 4 others contained both. Mitoses ranged from 0 to 68 per 10 high power fields (mean 4.7 per 10 high power fields). Tumors with benign cytomorphology or mild cytologic atypia (low-grade) were classified as myoepithelioma or mixed tumor, whereas tumors with moderate to severe atypia (high-grade) were classified as myoepithelial carcinoma (epithelioid or spindled cells with vesicular or coarse chromatin, prominent, often large nucleoli, or nuclear pleomorphism) or malignant mixed tumor (cytologically malignant cartilage or bone). Sixty-one cases were myoepitheliomas or mixed tumors, and 40 were myoepithelial carcinomas or malignant mixed tumors. By immunohistochemistry, all cases with available material were reactive for epithelial markers (keratins and/or epithelial membrane antigen): 90 of 97 (93%) expressed keratins (most often AE1/AE3 or PAN-K), 84 of 97 (87%) S-100 protein, 44 of 51 (86%) calponin, 52 of 83 (63%) epithelial membrane antigen, 40 of 87 (46%) glial fibrillary acidic protein, 27 of 75 (36%) smooth muscle actin, 15 of 66 (23%) p63, and 7 of 51 (14%) desmin. Follow-up was available for 64 patients. Among 33 cases with benign or low-grade cytology (mean follow-up 36 months; range 4-168 months), 6 recurred locally (18%) and none metastasized. No clinical or histologic features correlated with recurrence. Among 31 cytologically malignant cases (mean follow-up 50 months; range 4-252 months), 13 recurred locally (42%) and 10 metastasized (32%); so far, 4 patients have died of metastatic tumor. This study expands the spectrum of myoepithelial tumors of soft tissue to include myoepithelial carcinomas and malignant mixed tumors, which pursue an aggressive clinical course. Although the majority of morphologically benign or low-grade myoepithelial neoplasms of soft tissue behave in a benign fashion, there is an approximate 20% risk for local recurrence.

Benign spindle cell tumors of the mammary stroma: diagnostic criteria, classification, and histogenesis

Purely benign mesenchymal spindle cell neoplasms of the breast are currently labeled under various terms in the literature (benign spindle cell tumor, fibroma, spindle cell lipoma, myofibroblastoma, solitary fibrous tumor, myogenic stromal tumor). The lack of strict diagnostic criteria to clearly indicate such mesenchymal neoplasms is the main reason which generated the risk of terming the same lesion under different names or, conversely, of collecting different types under the same term. Although such neoplasms exhibit morphological and immunophenotypical heterogeneity, they actually represent variations of the same tumor entity, likely arising from the uncommitted vimentin+/CD34+ fibroblasts of the mammary stroma, capable of multidirectional mesenchymal differentiation. To cover the entire spectrum of such lesions, the term "benign spindle cell tumors (BSCTs) of the mammary stroma" is advocated. BSCTs can be subtyped into four main groups by light microscopy (LM) and immunocytochemistry (ICC): fibroblastic, myofibroblastic, fibrohistiocytic, and mixed forms. A simple and practical approach to a nosologically correct diagnosis and a list of differential diagnoses are presented. The awareness of the diversity of morphological and immunophenotypical features of BSCTs of the mammary stroma, including uncommon variants, is helpful to avoid confusion with other monomorphic bland-looking benign and malignant spindle cell tumors and tumor-like lesions of the breast.

Signet ring cell basal cell carcinoma: a basal cell carcinoma with myoepithelial differentiation

Basal cell carcinoma (BCC) can show a variety of routes of differentiation, but myoepithelial differentiation has rarely been described. We describe a case of BCC showing histologic and immunohistochemical features of myoepithelial differentiation. Histologically, the lesion showed well-demarcated tumor nodules composed of two different components. One component was typical of BCC, and the other component was composed of tumor cells containing abundant cytoplasm, eccentric nuclei, and no peripheral palisading, with scattered signet ring-shaped cells. Immunohistochemically, the tumor cells in the typical BCC component stained with CKAE1/AE3 and smooth muscle actin (SMA), but not with S-100 protein. They stained weakly with CAM5.2, epithelial membrane antigen, and glial fibrillary acidic protein (GFAP). The tumor cells in the other component stained strongly with CKAE1/AE3 and SMA, moderately with epithelial membrane antigen and GFAP, and weakly with CAM5.2. In a small area, the tumor cells stained with S-100 protein.

Benign myoepithelioma of the lung: a case report and review of the literature

This report describes a benign myoepithelioma of the lung that occurred in a 60-year-old woman. The patient had experienced hoarseness for 6 weeks, and a computed tomographic scan showed a nodule of approximately 2 cm in diameter at the peripheral portion of her right upper lung. Positron emission tomography showed no uptake of F-18 fluorodeoxyglucose in the nodule. Wedge biopsy of the lesion showed benign spindle cells arranged in a whorled pattern. The cells were positive for both cytokeratin and smooth muscle actin, which corresponded to the presence of tonofilaments and myofilaments that were identified ultrastructurally. The features of the present case of benign myoepithelioma that differ from features of previously reported benign and malignant cases of myoepithelioma in the lung are discussed in the report.

Myoepithelioma metastatic to the orbit

PURPOSE

To report a case of myoepithelioma metastatic to the orbit in an 11-year-old boy.

METHODS

Interventional case report. An 11-year-old white male with a history of resection of a left thigh mass 10 months previously presented with a painless, rapid swelling of the left upper eyelid. Computed tomography scan and incisional biopsy of the orbital mass were performed.

RESULTS

Immunohistochemical stains of the tumor in the left orbit and the previously resected mass were consistent with myoepithelioma. As a result of widespread metastases, the patient died 4 months after initial presentation to the eye clinic.

CONCLUSION

Myoepithelioma should be included in the differential diagnosis of neoplasms that can metastasize to the orbit in the pediatric age group.

Myoepithelioma presenting as a midline cystic tongue lesion: cytology, histology, ancillary studies, and differential diagnosis

Salivary gland myoepithelioma (ME) is a neoplasm derived from myoepithelial cells that lacks the ductal and broad mesenchymal differentiation seen in the vast majority of mixed tumors. This report describes the cytologic findings of a cystic ME presenting in the midline of the dorsal tongue, a site where no salivary glands are generally present. The tumor was well circumscribed and composed of sheets of monotonous epithelioid cells without ductal cells. The cells were positive for S-100 protein and ultrastructurally had features of myoepithelial cells. The fine needle aspiration (FNA) biopsy findings, differential diagnosis, histology, immunohistochemistry, and electron microscopic features of this interesting and uncommon neoplasm are presented. To the best of our knowledge, there have been no cytologic reports of ME of the tongue.

[Salivary gland myoepithelioma]

Myoepithelioma is a rare salivary gland tumor (less than 1%) which are usually located in parotid gland and minor salivary glands. Histology and immunohistochemical features of this tumors are reviewed. We report 2 cases arising in parotid and hard palate.

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.

Application of immunohistochemistry to the diagnosis of salivary gland tumors

A panel of antibodies composed of the cytokeratins (CKs), vimentin, and actin was applied to 114 minor salivary gland tumors to evaluate its diagnostic value. The results revealed that luminal cells of intercalated duct-like structures, such as those seen in pleomorphic adenoma, basal cell adenoma, adenoid cystic carcinoma, and epithelial-myoepithelial carcinoma, expressed CKs 7, 8, 14, and 19. The outer cells of these structures exhibited vimentin or vimentin plus muscle-specific actin, but rarely CK14, which is seen particularly in pleomorphic adenoma, in the tubular type of basal cell adenoma, and seldom in the tubular type of adenoid cystic carcinoma. Modified myoepithelial cells of pleomorphic adenoma and myoepithelioma exhibited a variable immunoprofile. CKs 7 and 8 were also observed in acinar cell adenocarcinoma and polymorphous low-grade adenocarcinoma with vimentin in the latter. CK13 was expressed only by canalicular adenoma and mucoepidermoid carcinoma cells. This study showed that the panel of antibodies employed is effective in distinguishing among salivary gland 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.

Myoepithelial carcinoma of the salivary glands: a clinicopathologic study of 25 patients

Salivary gland carcinomas displaying exclusively myoepithelial differentiation (myoepithelial carcinoma) are considered rare. Their histopathologic features, immunohistochemical profile, and clinical behavior are not well characterized. The authors reviewed the clinicopathologic features of 25 salivary gland tumors fulfilling two fundamental histologic criteria: unequivocally malignant and exclusively myoepithelial. For most of these, the original diagnosis was malignant mixed tumor. Thirteen men and 12 women aged 24 to 77 years (mean age, 55 yrs) participated in the study, and most presented with a painless mass. The parotid gland was the most common site (n = 15). Tumors ranged from 2.1 to 5.5 cm, arising either in association with a benign mixed tumor (n = 15) or de novo (n = 10). Histologically, all the tumors displayed infiltrative growth and most had a characteristic multinodular architecture with a cellular periphery and central necrotic/myxoid zones. Epithelioid, hyaline, spindle, clear, or mixed cell types were noted with accompanying myxoid and/or hyalinized extracellular matrix. Ten tumors were high grade cytologically and 15 were low grade. The mitotic rate ranged from three to 51 mitoses per 10 high-power fields. Necrosis was present in 15 tumors and perineural and vascular invasion were identified in 11 and four neoplasms respectively. Immunoreactivities included CAM5.2 (89%), AE1:AE3 (100%), 34betaE12 (92%), cytokeratin 7 (21%), cytokeratin 14 (53%), vimentin (100%), S-100 protein (100%), smooth muscle actin (50%), calponin (75%), muscle-specific actin (31%), glial fibrillary acidic protein (31%), carcinoembryonic antigen (0%), and epithelial membrane antigen (21%). Ultrastructural examination of three tumors showed myoepithelial features. Ten patients developed recurrences, mostly multiple. Follow up of 17 patients showed that eight patients (47%) developed metastases (six high grade, two low grade) and five patients (29%) died of disease (four high grade, one low grade) after a mean of 32 months. Two patients were alive with disease (19 and 49 mos). Ten patients (59%) were without any evidence of disease after a mean of 42.2 months. Myoepithelial carcinomas exhibit a wide spectrum of cytomorphologic features and diverse clinical outcomes. As a result of their morphologic heterogeneity, they can be confused easily with many tumors. Myoepithelial carcinomas have been underrecognized in the past, primarily by being lumped under a broader category of "malignant mixed tumor." Awareness of their unique cytoarchitectural patterns and immunohistochemical profile is crucial for accurate identification.

Myoepithelioma of the lung

A 54-year-old woman with myoepithelioma, a very rare tumor of the lung, is reported. The patient presented with exertional dyspnea, cough and intermittent pleuritic chest pain. Her chest X-ray revealed a peripheral 2 cm mass in the left lower lung zone. Bronchoscopy was normal. She underwent thoracotomy in which a wedge-resection was performed. Histological examination of the specimen demonstrated myoepithelioma of the lung.

Differential Expression of Myoepithelial Markers in Salivary, Sweat and Mammary Glands

Myoepithelial cells (MECs) are contractile elements showing a combined epithelial and smooth muscle phenotype. Among the numerous immunohistochemical markers employed to detect MECs, smooth muscle actin (SMA) is the most widely used. Recently, other markers of smooth muscle differentiation have been demonstrated in MECs, such as calponin, heavy caldesmon (h-caldesmon), and smooth muscle myosin heavy chain (SMM-HC). In the present study normal salivary, mammary, and sweat glands have been studied with four markers of smooth muscle differentiation (SMA, calponin, h-caldesmon, and SMM-HC). The four markers were differentially expressed in the various types of glands. In parotid glands MECs mainly expressed calponin and caldesmon; in submandibular and in cutaneous apocrine and eccrine glands, MECs strongly expressed SMA, calponin, and caldesmon; in minor salivary glands all four markers were equally strongly expressed; and in mammary glands SMA, calponin, and SMM-HC were present both in periductal and periacinar MECs while caldesmon was present in periductal MECs only. In addition to MECs, SMA stained stromal myofibroblasts, sometimes hampering the identification of MECs. Among the other markers, calponin stained only rare stromal myofibroblasts, while caldesmon and SMM-HC were confined to MECs. In conclusion, these latter markers are very useful for identifying MECs. It is suggested that the differential expression of smooth muscle contractile proteins might reflect different functions of MECs in the various sites. Int J Surg Pathol 8(1):29-37, 2000

A minor salivary gland tumour presenting with dysphagia

A case is reviewed of a giant benign myoepithelioma of the soft palate presenting in an elderly female patient. Due to the large size of the lesion and its mass effect the patient developed dysphagia with subsequent significant weight loss. The clinico-pathological features of this rare tumour are described and the literature reviewed.

Myoepithelioma of soft tissue

A myoepithelioma occurred in the subcutaneous tissue of the right shoulder of a 28-year-old man. The well-demarcated nodular tumor (3. 0 x 2.8 cm) was located in the subcutaneous tissue with no adhesion to the deltoid muscle. The tumor was composed of a fascicular proliferation of spindle cells with variable amounts of stroma and showed areas of sheets of epithelioid cells. In most areas, the tumor cells had uniform nuclei, but pleomorphic epithelioid cells were focally present. Mitotic activity was three per 10 high-power fields. No ductular structure was found throughout the tumor. Immunohistochemical and ultrastructural studies confirmed the myoepithelial origin of the tumor cells. The occurrence of myoepithelioma in the subcutaneous tissue has been rarely reported. Even though the tumor showed no aggressive behavior on the 2-year follow-up, it is still too early to comment definitely on the behav- ior of myoepithelioma of the subcutaneous tissue. This case provides further information about soft tissue myoepithelioma.

Immunoreactivity of ductal cells with putative myoepithelial markers: A potential pitfall in breast carcinoma

The identification of an intact layer of myoepithelial cells (MECs) located between epithelial cells and the basal lamina is useful in differentiating benign breast lesions and carcinoma in situ from invasive breast carcinoma. In the present study we used three antibodies considered to be putative markers of MECs (S100 protein, muscle-specific actin [HHF-35], and smooth muscle actin [SMA]) in 100 formalin-fixed, paraffin-embedded histologic sections of breast in an attempt to compare their value in demonstrating MECs in benign breast tissue and breast carcinomas. We concluded that for identifying MECs in benign breast tissue, SMA appears to be the most reliable, followed closely by HHF-35, but S100 is very unreliable for this purpose. In breast carcinoma, all three stains showed variable cross-reactivity with myofibroblasts, being greatest with SMA. A significant number of tumor cells in ductal carcinoma, both intraductal and invasive, stain with these markers and this "cross-reactivity" is extremely high with HHF-35. Thus, immunohistochemistry should be interpreted cautiously in differentiating benign, in situ, and invasive breast neoplasms. The "cross-reactivity" also suggests the possibility of myoepithelial differentiation and/or high actin content of breast tumor cells.

Atypical plasmacytoid monomorphic adenoma of salivary glands of the tongue: cytologic, histologic, immunohistochemical, and ultrastructural findings

We describe the case of an 11-yr-old boy with a 2.5-cm-diameter soft tumor superficially located at the dorsal aspect of the tongue. Fine-needle aspiration cytology smears showed plump epithelioid cells with round to mildly oval nuclei and open chromatin. One or two nucleoli of intermediate size were noticed in each nucleus. These cells appeared singly or in small groups. The findings were interpreted as containing plasmacytoid cells coming from an adenoma of salivary gland origin. The histologic examination of the surgical specimen revealed noncohesive, pleomorphic polygonal cells combining plasmacytoid/rhabdoid cytoplasmic features, with mild to moderate nuclear pleomorphism. One mitotic figure was observed per 10 high-power fields. Immunoreactivity was strongly positive for vimentin and S-100 protein, less intense for the cytokeratins, and negative for smooth muscle actin, muscle-specific actin, myoglobin, and GFAP. No ultrastructural evidences of myogenous differentiation were found. We propose that this case represents an unusual atypical variant of plasmacytoid monomorphic adenoma.

Electron microscopy in tumor diagnosis: indications for its use in the immunohistochemical era

The electron microscope reveals much more information on tumor cell structure than can be obtained with the light microscope, and some of the data are useful in diagnostic studies. In this review, major contributions of electron microscopy in the main tumor categories are discussed. To select between immunocytochemistry and electron microscopy, the probable contributions of each in the context of the particular case must be assessed. Usually, electron microscopy will only be requested after a battery of immunostaining procedures has been performed and found to be insufficient, but there are occasions when ulstrastructural study is logically the first choice after routine light microscopy. It is worth taking tissue for possible electron microscopy from any tumor that is known or anticipated to be a diagnostic problem.

Parotid gland tumors: histologic reevaluation and reclassification of 478 cases

BACKGROUND

The histologic classification of epithelial salivary gland tumors may present difficulties due to their great morphologic diversity.

METHODS

In this study, 478 parotid gland tumors were reevaluated and reclassified according to the 1991 WHO histologic classification of salivary gland tumors.

RESULTS

In 56 cases, the original diagnosis was changed, either within the benign or the malignant tumor group. In six cases (1.3%), the original diagnosis was changed from benign to malignant or vice versa.

CONCLUSIONS

During the mean follow-up period of 10.3 years, no events occurred supporting or rejecting the proposed change in diagnosis in these six patients. With regard to the three cases in which an original malignant diagnosis was made, the possibility of an overdiagnosis, and therefore an overtreatment, remains.

Malignant plasmacytoid myoepithelioma of the palate: histological observations compared to benign predominant plasmacytoid myoepithelial cells in pleomorphic adenoma of the palate

Predominant benign plasmacytoid myoepithelial cells in pleomorphic adenoma and malignant plasmacytoid myoepithelioma cells were investigated morphologically. The cells of both tumors were plasmacytoid in appearance and sheet-like. Immunohistochemically, they were positive for keratin, vimentin, and S-100 protein, and negative for alpha-smooth muscle actin. In the malignant cells, large nuclei with irregular nuclear membranes and distinct nucleoi and occasional intranuclear inclusions and nuclear grooves were seen. Ultrastructural findings showed that the benign cells were richer in intermediate filaments and had fewer mitochondria. The intranuclear inclusions and nuclear grooves of the malignant cells were caused by invagination of the irregular nuclear membranes. Taken in their entirety, the above light microscopical nuclear findings may be useful as an adjunct for distinguishing malignant from benign plasmacytoid neoplastic myoepithelial cells of the salivary gland.

Expression of smooth-muscle actin in cultured cells from human plasmacytoid myoepithelioma

OBJECTIVE

The definition of plasmacytoid myoepithelioma, a neoplasm exhibiting myoepithelial differentiation, has been recently questioned. To better understand the histogenesis of this neoplasm, we searched for myoepithelial markers in histologic sections of plasmacytoid myoepithelioma and in a cell line (M1) derived from this same neoplasm.

STUDY DESIGN

Expression of vimentin, pan-keratin (AE-3) and smooth-muscle actin was studied by immunohistochemistry in paraffin-embedded tissue and by immunofluorescence in M1 cells.

RESULTS

Plasmacytoid myoepithelioma tumor sections showed vimentin and AE-3 reactivity, but evidence of smooth-muscle actin was not seen. The cell line derived from this tumor also produced vimentin and cytokeratin. In addition, all cultured cells expressed smooth-muscle actin.

CONCLUSION

We demonstrated that cells derived from a case of plasmacytoid myoepithelioma appear to show full myoepithelial differentiation in vitro. Thus, they are myoepithelial-like cells in nature. The lack of myogenous differentiation in vivo could be due to an inhibitory process mediated by the extracellular matrix.

Mixed tumors and myoepitheliomas of soft tissue: a clinicopathologic study of 19 cases with a unifying concept

We report 19 unusual cases of mixed tumors and myoepitheliomas arising in soft tissues. The neoplasms occurred in 12 males and seven females. The age at diagnosis ranged from 2 to 83 years (mean 35, median 30). Eight tumors arose in the upper limb, six in the lower limb, three in the trunk, and two in the head and neck region. Three cases involved both dermis and subcutis; the remainder arose in subcutaneous (13 cases) or deep subfascial soft tissue (three cases). The most common presenting complaint was a painless swelling, with duration ranging from 2 weeks to 1 year (median 2.5 months). Microscopically, the tumors were predominantly well circumscribed and lobulated. Six cases showed a focally infiltrative margin. Cardinal morphologic features included nests, cords, and ductules of epithelioid cells and/or nests of spindled cells within a hyalinized to chondromyxoid stroma. One tumor was predominantly composed of myoepithelial cells and devoid of epithelial differentiation (i.e., ductules). Cytoplasmic hyaline inclusions were noted in two cases; squamous differentiation was seen in one case. Osteoid production and/or metaplastic bone was observed in three tumors. Chondroid differentiation (usually mature) was seen in four cases. Adipocytic differentiation was seen in two tumors. Mitotic activity was variable but generally scant; atypical mitotic figures were not identified. By immunohistochemistry, 16 of 16 cases expressed pan-keratin; 16 of 17 S-100 protein; six of 14 alpha smooth muscle actin (IA4); two of 10 muscle specific actin (HHF-35); two of 10 desmin; three of 11 glial fibrillary acidic protein; and three of 16 epithelial membrane antigen. Clinical follow-up was available in 10 patients and ranged from 6 months to 20 years (mean 4.25 years, median 2 years). Two patients developed local recurrence; metastasis to lung and lymph nodes were observed in two additional patients. Both of the latter patients died. We believe that these findings expand the concept of cutaneous mixed tumors to include neoplasms composed predominantly of myoepithelial cells and to include tumors arising in deeper subcutaneous and/or subfascial tissues. The clinical behavior of such neoplasms, when arising in soft tissues, may be difficult to predict but is most often benign; however, a minority of lesions metastasize. Until larger studies with longer follow-up are available, treatment and prognostication are probably best based on criteria used in comparable salivary gland tumors.