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.     

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.     

涎腺透明细胞肌上皮癌和透明细胞癌的临床病理比较分析

目的：探讨涎腺透明细胞肌上皮癌和透明细胞癌的临床病理与免疫组化特征。方法：回顾分析武汉大学口腔医学院口腔病理科1985～2008年期间确诊的3例透明细胞肌上皮癌和5例透明细胞癌。常规HE染色和免疫组化（CKAE1/AE3,S100,vimentin,smooth muscle actin,calponin,P63和maspin）做比较观察。结果：两种肿瘤几乎全部由透明细胞构成,在透明细胞肌上皮癌中可见少量梭形细胞,透明细胞癌中可见少量含有嗜酸性胞浆的细胞。免疫组化显示：透明细胞肌上皮癌中,3例均阳性表达CKAE1/AE3,S100,vimentin,P63和maspin,2例阳性表达smooth muscle actin和Calponin;透明细胞癌中,5例均阳性表达CKAE1/AE3,P63和maspin,而S100,vimentin,smooth muscle actin,calponin均呈阴性表达。结论：涎腺透明细胞肌上皮癌和透明细胞癌都很罕见,二者可通过组织病理和免疫组化特点进行鉴别。由于肿瘤性肌上皮细胞可呈现不同的肌源性分化,因此联合运用多种提示肌上皮源性的标志物如CKAE1/AE3,S100,vimentin,smooth muscle actin和calponin对二者鉴别诊断有帮助。P63和maspin缺乏特异性。     

Epithelioid myoepithelioma of the hard palate

Background

Myoepithelioma, a generally benign tumor comprised of myoepithelial cells, is an uncommon salivary gland tumor. Among four morphologic variants of myoepithelioma, epithelioid type has not been reported in the oral and maxillofacial region.

Case report

A 61-year-old man first noticed the mass 3 years previously. The oral examination revealed a firm, non-tender, and well-circumscribed mass in the middle of the hard palate. A magnetic resonance imaging scan showed a well-circumscribed mass with low signal intensity (T₁-weighted image) or increased signal intensity (T₂-weighted image).

Discussion

Immunohistochemically, the tumor cells in the present case reacted to the epithelial (CK HMW and CAM5.2) and the mesenchymal (vimentin) markers. However, myoepithelial markers (S-100 protein, α-smooth muscle actin, glial fibrillary acidic protein, and calponin), except p63, were not expressed in the tumor cells. These results indicated that the epithelial myoepithelioma cells differentiated into epithelial cells rather than myoepithelial cells. We believe that epithelioid myoepithelioma of the palate is a distinctive subtype of myoepithelioma that should be included in the differential diagnosis of tumors of the palate.     

金属硫因蛋白在涎腺肿瘤中的表达及意义

为了研究金属硫因蛋白在涎腺肿瘤中的表达特点，作者用免疫组织化学方法对７５例涎腺肿瘤进行了研究。在腺上皮和肌上皮混合构成的肿瘤，如：腺样囊性癌、多形性腺瘤、腺上皮肌上皮癌、基底细胞腺瘤（癌）等，金属硫因蛋白只在肌上皮细胞中表达并且均有较强染色。肌上皮癌和肌上皮瘤中有相当多的细胞表达金属硫因蛋白。抗金属硫因蛋白单克隆抗体对肌上皮细胞的染色在部分病例较Ｓ－１００蛋白和平滑肌动蛋白效果好。本结果表明，金属硫因蛋白可能成为涎腺肿瘤性肌上皮细胞较好的标志，有助于涎腺肿瘤的鉴别诊断。     

Plasmacytoid myoepithelioma of the palate

We present the second case of plasmacytoid myoepithelioma of the palate, which was studied by light and electron microscopy. Apart from plasmacytoid cells, some spindle-shaped cells were also observed. Both types of neoplastic cells had myoepithelial features, showing abundant 50–80 A thick filaments in the cytoplasm, and exhibited desmosomal junctions. A few light cells with less abundant filaments and better equipped with other organelles were observed.
Our findings show that there is no clear-cut distinction between the so-called plasmacytoid myoepithelioma and the spindle and stellate myoepithelioma. We suggest that the ultrastructural appearance of these tumors together with the usual histological criteria for malignancy may be used to evaluate their prognosis.     

Myoepithelioma arising from the buccal gland: histopathological and immunohistochemical studies

A rare case of myoepithelioma of the buccal gland in a 54-year-old Japanese woman is reported. As the swelling exhibited a normal mucosal color and was relatively well defined, showing no ulcers, a benign salivary gland tumor was suspected upon clinical inspection. Microscopically, the parenchyma of the present case mainly consisted of plasmacytoid cells with round nuclei and eosinophilic cytoplasm, and partial spindle cells with eccentric nuclei. The stroma was composed of fibro-hyalinized or myxoid connective tissue that separated from the parenchyma. Immunohistochemically, the cytoplasm of the plasmacytoid and spindle cells was moderately positive for vimentin and GFAP, whereas the buccal gland adjacent to the tumor was negative for these antibodies. S-100 protein reactivity is strong for both types tumor cells. Actin reactivity was negative for both types of tumor cells, notwithstanding the fact that myoepithelial cells of the buccal gland were positively stained. Anti-cytokeratin reactivity was weak for both types of tumor cells in portions of the plexiform and solid areas; nevertheless, the buccal glands were moderately positive. These results suggest that neoplasmic myoepithelial cells exhibit abnormal differentiation and modification. There have been only two published reports of myoepithelioma arising from the buccal gland in the literature to date.     

Actin versus vimentin in myoepithelial cells of salivary gland tumors: A comparative study

Vimentin versus actin expression was immunohistochemically studied in myoepithelial cells of 24 salivary gland tumors in which the participation of myoepithelial cells as a tumoral component has been postulated: two basal cell adenomas, seven pleomorphic adenomas, two myoepitheliomas, seven adenoid cystic carcinomas (two tubular, four cribriform, one solid), six polimorphous low-grade adenocarcinomas. Immunostaining was carried out in formalin-fixed tissue serial sections (3 μm) by the avidin-biotin method, using the antibody vimentin (Dako Corp., Carpenteria, Calif.) and the antibody HHF35 anti-muscle actin (Enzo Biochemical, N.Y.). Our results have confirmed positive staining for vimentin in all salivary tumors studied, although in some tumors it was only in focal areas. The staining for the HHF35 antibody to muscle actin was only consistently found in the adenoid cystic carcinomas of the tubular and cribriform patterns. This study suggests that actin is at least somewhat replaced by vimentin in neoplastic tumoral cells. Therefore vimentin can be used to define the participation and distribution of myoepithelial cells in these tumors.     

涎腺肌上皮瘤的临床病理分型和免疫组化研究

对从１８７３例涎腺肿瘤复查后确诊的４３例涎腺肌上皮瘤进行了临床病理学和免疫组化研究。结果显示：该瘤的患病率约占涎腺肿瘤的２．３％，好发于腮腺（４８．８４％）和腭腺（４１．８６％）；该瘤在病理上可分为５型：即上皮细胞型、梭形细胞型、浆细胞样细胞型、透明细胞型和混合细胞型，其实质细胞——肿瘤性肌上皮细胞为一个连续变化的瘤细胞谱，各种形态的瘤细胞可以互相转化；免疫组化ＣＫ－１８、ａｃｔｉｎ染色显示上述各型瘤细胞均为程度不等的阳性。作者认为提高该瘤确诊率的关键是对各型瘤细胞的认识；联合应用ＣＫ－１８、ａｃｔｉｎ有助于该瘤的诊断和与多形性腺瘤的鉴别。     

Product definition in a case of myoepithelioma

One case of myoepithelioma was studied by immunohistochemical and histochemical methods to identify the cell products of this tumor. The myoepithelioma had two cell types: plasmacytoid cells and spindle cells. The tumor myoepithelial cells produced the same cell products as did the normal myoepithelial cells but in variable amounts, possibly related to stages of differentiation. As no exocrine cell products could be identified in this neoplasm, it is considered a "true" myoepithelioma.     

涎腺原发恶性肌上皮瘤19例的病理诊断分析

目的 探讨涎腺多结节形态原发恶性肌上皮瘤的病理特征。方法 光镜观察19例涎腺多结节形态原发恶性肌上皮瘤的组织学、细胞学结构,其中11例做Calponin、平滑肌肌动蛋白(SMA)、S-100、神经胶质酸性蛋白(GFAP)、细胞角蛋白、增殖细胞核抗原(PCNA)的免疫组化检测,3例做超微结构观察。结果 肿瘤上皮巢呈多结节生长,中央常伴坏死,肿瘤侵袭周围组织,细胞有异形,肿瘤细胞主要为上皮样细胞型,有较多肿瘤性基质形成。肌上皮性标记及部分细胞角蛋白、PCNA标记阳性。电镜下见肿瘤细胞内有肌微丝。结论 免疫组化染色及超微结构观察均支持肿瘤为肌上皮来源及恶性特征。     

涎腺肌上皮瘤31例临床病理学分析

目的 分析涎腺肌上皮瘤(myoepithelioma,ME)临床病理学特点及生物学行为。方法 对1992年1月至2000年8月收治的31例患者进行回顾性分析。结果 ME主要发生于腮腺及腭部。临床上表现为无痛性缓慢生长的包块,无面瘫及破溃。光镜下呈实性、黏液性、网状或混合性生长方式。肿瘤细胞有梭形、浆细胞样、透明细胞样、上皮样型或混合型。4例肿瘤细胞生长活跃,在侵袭性生长的病例中可见轻度的细胞异型性、有丝分裂增加及包膜浸润。所有病例均采用手术切除。28例患者术后无复发。3例肿物复发或恶变为肌上皮癌。结论 ME是一类少见的肿瘤,具有独立的临床病理学特点,部分肿瘤侵袭性生长并具有潜在恶性的特点。     

Hyalinizing clear cell carcinoma of minor salivary gland: case report

Hyalinizing clear cell carcinoma is a low-grade neoplasm of the minor salivary gland composed exclusively of epithelial cells and not myoepithelial cells. It predominantly affects the oral cavity of adult females. It is microscopically characterized by hyalinizing stroma and clear cells, which are typically positive for cytokeratin markers and negative for S 100 and smooth muscle actin (SMA). Cystic degeneration can also be present. Pathologists should be aware of this new entity so as not to misdiagnose otherwise. To our knowledge, this is the first case report of its kind from Malaysia.     

Adenoid cystic carcinoma of the salivary glands: an immunohistochemical analysis

Adenoid cystic carcinoma is a specific variant of adenocarcinoma with a characteristic cribriform appearance. The tumor may arise from salivary glands and various other sites, but the origin and cellular composition of this unique neoplasm have been controversial. A potential use of immunohistochemistry is to provide additional information on the origin of various cellular components of tumors by comparing them with corresponding normal tissues. Immunohistochemical distributions of carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), keratin, low molecular weight keratin (54 kd), S100 protein, muscle-specific actin, laminin, and type IV collagen were evaluated in 20 adenoid cystic carcinomas arising in major and minor salivary glands. Anti-CEA, anti-EMA, anti-keratin, and anti-S100 antibodies strongly stained cells lining true lumina. Muscle-specific actin, a marker for myoepithelial cells, was found in lining cells of pseudocysts, in tumor cells proper, and in nonluminal cells with a tubular growth pattern. A monoclonal antibody against 54 kd keratin stained almost all cells in the neoplasms. In pseudocysts, replicated basal lamina reacted with antisera to laminin and to type IV collagen. The present study demonstrates that there are at least two populations of tumor cells in adenoid cystic carcinoma: luminal cells that express CEA and EMA, thus indicating their ductal character, and nonluminal cells that express muscle-specific actin characteristic of myoepithelium.     

Magnetic resonance imaging of myoepithelioma in the salivary glands

Myoepithelioma is a rare benign tumor composed of cells showing myoepithelial differentiation and accounts for only 1.5 % of all tumors in the major and minor salivary glands. Herein, we report the magnetic resonance imaging (MRI) findings, including dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted MRI (DW-MRI), of two cases of myoepithelioma occurring in the salivary glands of the floor of the mouth and the hard palate. Both tumors were seen as well-defined ovoid masses with low or intermediate signal intensity on T1-weighted images, and inhomogeneous high signal intensity areas on T2-weighted images, whereas inhomogeneous enhancement was seen on post-contrast T1-weighted images. On DCE-MRI, both tumors showed a time–intensity curve of early enhancement and a low washout pattern (plateau enhancement pattern). Their apparent diffusion coefficients measured on DW-MRI were both relatively low (1.12 × 10^?3 and 0.76 × 10^?3 mm²/s). The findings for these two myoepitheliomas on DCE-MRI and DW-MRI were dissimilar to those in previous reports.     

Malignant myoepithelial carcinoma (myoepithelioma) arising in a pleomorphic adenoma of the parotid gland. An immunohistochemical study and review of the literature

A 66-year-old woman presented with a giant tumor of the parotid gland, which under a light microscope had a sarcomatous appearance with spindle-shaped myoepithelial cells (malignant myoepithelioma). Histochemical examination showed longitudinal fibrils in the cytoplasm of the myoepithelial cells. Immunohistochemical studies showed positive staining for S-100 protein, vimentin, and actin in the myoepithelial cells. Cytokeratin was seen in the ductular epithelial cells and in the periductular myoepithelial cells, but it was absent from malignant myoepithelial cells. Ultrastructurally, these cells contained several longitudinally oriented slender structures resembling myofilaments without dense bodies. A review of the literature confirms the rarity of malignant myoepithelial carcinoma (myoepithelioma) arising in the parotid gland, and we therefore add another case.     

Histologic evaluation of myoepithelial participation in salivary gland tumors

To evaluate the myoepithelial participation in various salivary gland tumors, 40 cases were studied using the tannic acid--phosphomolybdic acid--Levanol fast cyanine 5RN (TPL) method directly correlated with ultrastructural observation. The TPL positivity corresponded to cytofilaments, especially microfilaments within the cells showing myoepithelial features. This approach allowed categorization of the examined tumor types into the following 4 groups according to the degree of myoepithelial participation: tumors with major myoepithelial, epithelial-myoepithelial (biphasic), minor myoepithelial, and no myoepithelial participation. It is suggested that the first 2 categories form a spectrum with myoepithelioma and basal cell adenoma at the extremes, in which neoplastic myoepithelial cells assume an active and integral constitutive r?le. The present findings indicate that the TPL method offers a very reliable marker for the screening of neoplastic myoepithelium in salivary gland tumors and thus may help in subclassification on a histogenetic basis for these tumors.     

Histolgical and immunohistochemical study of malignant myoepithelioma of salivary glands]

Histological and immunohistochemical features of 12 cases of malignant myoepithelioma of the salivary glands were studied.There were 4 major histologic types in the tumor tissues:(1)clear tumor cells proliferated mainly with or without keratin peral;(2)spindle shaped tumor cells proliferated mainly with or without mucoid regions;(3)plasmacytoid(hyaline) tumor cells were arranged in adenoid configurations.In the immunohistochemical studies,the tumor cells were positive for actin;myosin;glial,fibrillary,acidic,protein.(GFAP);S-100 protein antibodies.The authors consider that the application of the above-mentioned antibodies may assist in the differentiated diagnosis of malignant myoepithlioma.     

Pleomorphic Adenoma (Benign Mixed Tumour) of the Minor Salivary Glands of the Upper Lip

Pleomorphic adenoma is the benign tumor of salivary glands, which originates from the myoepithelial cells and intercalated duct cells. This tumor is more common in major salivary glands. This case report describes a rare and unusual lesion in a 55-year-old female, which was diagnosed as pleomorphic adenoma of the minor salivary glands in the upper lip. The tumor was a circumscribed, submucosal nodule, about 2.0 cm in diameter and was characterized by slow growth and rubbery consistency. Complete excision was performed and the histopathological analysis showed an epithelial salivary gland tumor with islands of plasmacytoid cells, duct like structures, in a variable stroma with chondroid, fibrous and myxoid appearance. No recurrence was observed 1 year after the surgery.     

Sialadenoma papilliferum: an immunohistochemical study of five cases

Sialadenoma papilliferum (SP) is a rare, benign, salivary gland tumor which most commonly arises in the palate. It has a typical biphasic gross and microscopic appearance which distinguishes this tumor from other papillary-like tumors of the oral cavity. This study reports the clinico-pathologic features of 5 new cases and analyzes the morphologic and immunophenotypic features of their cell components. Adluminal epithelial cells of duct-like structures appeared immunoreactive to cytokeratin 19 and to S-100 protein antibodies; two subsets of basally-located cells were identified by means of immunohistochemistry. One cell subset expressed cytokeratin 14, S-100 protein. GFAP, vimentin and smooth muscle actin immunoreactivity: this antigenic profile is consistent with myoepithelial differentiation. The second subset of basal cells expressed eytokeratins 13 and 14 reactivity' but it was negative to all other antibodies. Anti-CD la and anti-S-100 protein antibodies revealed distinct cells with dendritic processes which resembled Langerhans cells. The extralobular location of SP, the continuity between neoplastic duct-like structures and the surface epithelium along with the presence, within the excretory ducts adjacent to the tumour, of lesions which possibly precede the development of SP give further strength to the hypothesis of an origin from the excretory ducts of this tumor. Langerhans cells seem to be present in Sialadenoma papilliferum but their role in this tumor is still unclear.