Primary leiomyosarcoma of bone

Four cases of primary leiomyosarcoma of bone are presented. The histology of this rare tumour has been studied with a panel of monoclonal antibodies to the intermediate filaments desmin and vimentin, and to other markers including smooth muscle actin, myosin, alpha 1-antitrypsin, alpha 1-antichymotrypsin, lysozyme, S-100 protein and cytokeratin. The tumour cells were uniformly positive for desmin, vimentin, and in one case for smooth muscle actin; all the other markers were negative. The findings have been compared with other spindle cell lesions of bone and with electron-microscopy of the tumours. Immunohistochemistry allows the histological diagnosis to be made without the need to resort to ultrastructural studies.     

Biochemical evidence that cytokeratins are present in smooth muscle

Recent immunocytochemical studies have revealed that cytokeratin intermediate filaments, previously thought to be restricted to epithelial tissues, are present in muscle. In view of the implications of these reports for diagnostic pathology it is important to investigate by biochemical means whether these findings represent the presence of true cytokeratin proteins or an unexpected antigenic cross-reaction. In the present study intermediate filament proteins have been extracted from samples of human myometrium and identified by immunoblotting techniques using well characterized monoclonal antibodies, two against cytokeratins and two against desmin. The results show that the proteins of the appropriate molecular weight for cytokeratin were labelled by anti-cytokeratin antibodies and were quite distinct from those recognized by anti-desmin antibodies. This study therefore confirms previous immunocytochemical findings and emphasizes the need for caution when using anti-intermediate filament antibodies for diagnostic purposes.     

Biochemical evidence that cytokeratins are present in smooth muscle.

Recent immunocytochemical studies have revealed that cytokeratin intermediate filaments, previously thought to be restricted to epithelial tissues, are present in muscle. In view of the implications of these reports for diagnostic pathology it is important to investigate by biochemical means whether these findings represent the presence of true cytokeratin proteins or an unexpected antigenic cross-reaction. In the present study intermediate filament proteins have been extracted from samples of human myometrium and identified by immunoblotting techniques using well characterized monoclonal antibodies, two against cytokeratins and two against desmin. The results show that the proteins of the appropriate molecular weight for cytokeratin were labelled by anti-cytokeratin antibodies and were quite distinct from those recognized by anti-desmin antibodies. This study therefore confirms previous immunocytochemical findings and emphasizes the need for caution when using anti-intermediate filament antibodies for diagnostic purposes.     

Cytokeratins, smooth muscle actin and vimentin in human normal salivary gland and pleomorphic adenomas. Immunohistochemical studies with particular reference to myoepithelial and basal cells.

The distribution of immunostaining in normal major salivary gland and in 12 pleomorphic adenomas was studied using monospecific monoclonal antibodies to a number of cytokeratins, including cytokeratin 14, to smooth muscle actin and vimentin. A number of these antibodies enabled a distinction to be made between structural components of the normal gland, and to relate this to the different structures of pleomorphic adenomas. In the normal gland, the luminal duct cells expressed cytokeratins 7, 8, 18 and 19. Three antibodies were of particular value for the characterization of normal myoepithelial and basal cells; while the antibody to smooth muscle actin and the cytokeratin antibody Ks8.12 mutually exclusively stained the myoepithelial (basket) cells and the basal duct (light) cells, respectively, the recently established monospecific antibodies to cytokeratin 14 showed specific immunostaining with both cell types. These three antibodies left luminal cells virtually unstained. Ck 13 was found occasionally in single luminal excretory duct cells. Antibodies to cytokeratins 1/2, 10 and 10/11 did not show any staining in the normal gland. In the pleomorphic adenomas, the staining pattern of the two-layered tubular formation resembled that of the normal gland ducts: tumour luminal cells showed the characteristic, although more irregular, expression of cytokeratins 7, 8, 18 and 19; the outer cells resembled normal ductal basal cells with their anti-cytokeratin 14/Ks8.12-epitope staining and in that they virtually lacked staining for smooth muscle actin. Trabecular formations and cells in myxoid areas were reactive with Ks8.12 and for cytokeratin 14, occasionally also for cytokeratins 7, 18 and 19. Epidermoid cell islets expressed mainly cytokeratin 14 and inconsistently the squamous epithelial cytokeratin 13 and the epidermal cytokeratin 10/11. Vimentin was found in cells of myxoid areas. The results support the postulate that some of the normal duct basal cells act as reserve cells and can give rise to tumour formation with a primitive myxoid or trabecular pattern and a more differentiated tubular or epidermoid configuration.     

Intermediate filaments in smooth muscle tumours

Antisera to the intermediate filaments vimentin and desmin react with fixed paraffin embedded tissue. Benign uterine myomas contain both classes of filaments. Gastrointestinal "smooth muscle tumours" however often lack desmin even when they appear histologically benign. In the sarcomas examined vimentin was the only class of intermediate filament present. The diagnostic and histogenetic implications of these findings are discussed.     

Coexpression of intermediate filament polypeptides in human fetal and adult tissues

Tissues from human fetuses (12 to 14 weeks) were studied by using immunohistochemical methods, with special emphasis on coexpression of intermediate filaments. Well-characterized antibodies, monoclonal as well as polyclonal were used. Indirect immunoperoxidase staining disclosed simultaneous expression of cytokeratin and vimentin, or vimentin and desmin in several tissues, whereas some other tissues coexpressed three classes of intermediate filaments, i.e., cytokeratin, vimentin, and desmin. Coexpression of cytokeratin and vimentin was seen in immature tubules of the kidney localized in the blastema and in one case in a small area of the epithelium of the tongue. Coexpression of vimentin and desmin was found in stromal cells of the medulla of the kidney, in stromal cells of the decidua (maternal tissue) and in muscle cells in blood vessels of small intestine, kidney and decidua. Coexpression of cytokeratin, vimentin, and desmin was present in mesothelial cells of serosa, pleura and pericardium, in stroma of umbilical cord and placental villi, in muscle cells of small intestine, tongue, and heart, and in muscle cells of blood vessels of lung, heart, umbilical cord, and placental villi. Mesothelium and reactive submesothelial stroma cells also coexpressed three classes of intermediate filament polypeptides. In some cases, immunoperoxidase results were confirmed by double labeling immunofluorescence microscopy or by immunoblotting experiments. The results of this study indicate that coexpression of different types of intermediate filaments is a more general phenomenon in fetal tissues than previously realized and it also occurs in some reactive proliferative lesions in the adult.     

Expression of intermediate filament proteins in normal and diseased thyroid glands.

A total of 67 samples from normal and pathological thyroid glands were stained (as formalin fixed paraffin sections) with a panel of monoclonal antibodies directed against intermediate filament proteins. The study confirmed previous reports of cytokeratin and vimentin coexpression in primary thyroid carcinomas, but coexpression was also detected in normal thyroid and in a range of benign conditions including follicular adenomas, Hashimoto's thyroiditis, and diffuse hyperplasia (thyrotoxicosis). Prekeratin expression was found (using antibodies recognising higher molecular weight cytokeratins) predominantly in areas of squamous change, independent of the underlying thyroid pathology. This study does not therefore support previous findings that prekeratin expression provides a reliable means of distinguishing follicular pattern papillary carcinoma from follicular carcinoma with its poorer prognosis or that it helps distinguish benign from malignant papillary lesions. No evidence of desmin or neurofilament expression was seen, and in particular, neurofilaments could not be detected in any of the cases of medullary carcinoma studied.     

Transient cytokeratin expression in skeletal muscle during murine embryogenesis.

Cytokeratin expression was investigated in paravertebral skeletal musculature of 10 d and 18 d old embryos as well as in adult NMRI-mice. The muscular nature of the evaluated tissue was evidenced by their expression of vimentin and desmin. Binding moieties for cytokeratin antibodies (polyclonal and monoclonal) could be demonstrated only in muscle cells of 10 d old embryos. Concerning subtypes, the mouse equivalents of the human cytokeratins Nos. 8, 18 and 19 could be made probable. The importance of the transient cytokeratin expression in murine embryonal skeletal muscle cells is emphasized, because this intermediate filament type is expressed in rhabdomyosarcomas too.     

Coexistence of cytokeratin,vimentin and neurofilament protein in human choroid plexus

Summary The expression of intermediate filament proteins in human brain ependyma and choroid plexus epithelium has been studied by immunohistochemistry using a panel of monoclonal antibodies directed against all five classes of intermediate filaments. Ependymal cells express GFAP and vimentin filaments, whereas plexus epithelium simultaneously contains neurofilaments, cytokeratins and vimentin, a phenomenon not previously observed in normal cells in vivo. By means of specific antibodies we were able to establish that cytokeratins 8 and 18 but not 19 are present in plexus epithelium.     

Smooth muscle cells of neural crest origin form the aorticopulmonary septum in the avian embryo

Previous studies have shown that the cells of the aorticopulmonary (AP) septum are similar to the smooth muscle cells of the mediae of the great vessels in their common origin from the cardiac neural crest and in their common expression of an elastic extracellular matrix. The purpose of this study was to test the cells of the AP septum for the presence of certain cytoplasmic proteins, especially smooth muscle alpha-actin (SMAA) whose presence is definitive of smooth muscle. A monoclonal antibody against SMAA was applied to normal chicken embryos at 3.5–8 days of incubation and to age-matched embryos from which the cardiac neural crest had been ablated surgically. Antibodies against the intermediate filaments desmin, cytokeratin, and vimentin also were applied. The results showed that the AP septal cells expressed SMAA during the process of septation, days 5–8; but when the cardiac neural crest was ablated and septation was defective, no cells in the conotruncal connective tissue expressed SMAA. None of the intermediate filament proteins were detected in the septum. These results indicate that the AP septal cells are smooth muscle and therefore may be hypothesized to have an active role in septation.     

The detection of smooth muscle antibodies reacting with intermediate filaments of desmin type

Some human smooth muscle antibodies (SMA) react with cytoskeletal intermediate filament (IMF) antigens. The smooth muscle tissue contains two types of IMF: vimentin and desmin filaments. In this study, SMA of anti-IMF type in 52 patients' sera have been classified into anti-vimentin filament and anti-desmin filament types according to their immunofluorescence staining patterns on rat testis. This classification is based on the fact that the arterial walls of testis contains both vimentin and desmin whereas the myoid cell layer surrounding the seminiferous tubuli contains only desmin. Four out of the 52 sera gave the anti-desmin staining pattern and 40 sera showed the anti-vimentin type of staining. Thirty-two sera were further classified by using cultured human rhabdomyosarcoma (RD) cells as targets. Nine sera reacted with the intermediate filaments of the RD cells. Among these were 3 out of the 4 sera that gave the anti-desmin filament staining pattern. The anti-desmin specificity of SMA was confirmed in 1 serum by the immunoblotting technique. These results indicate that while human anti-desmin filament antibodies exist, most human SMA of anti-IMF type react with vimentin filaments.     

Co-expression of cytokeratin and vimentin intermediate-sized filaments in renal cell carcinomas

Summary The expression of intermediate-sized filaments (IF) was examined by immunocytochemical methods in 40 primary renal cell carcinomas and compared with the IF distribution in the normal adult human kidney. All tumours stained positively with cytokeratin IF antibodies. Co-expression of cytokeratins and vimentin was observed in 21/40 (52,5%) renal carcinomas. Double immunofluorescence labelling demonstrated that in most of these cases tumour cells contained both cytokeratin and vimentin type IF. In normal human kidneys, cells of the various tubular segments disclosed a positive reaction with cytokeratin antibodies in a different intensity and intracellular localization. Co-expression of cytokeratin and vimentin IF in normal adult human kidneys has never been observed. From a histogenetic point of view, co-expression of cytokeratins and vimentin in renal cell carcinoma obviously represents an atavistic phenomenon since vimentin is re-expressed by these tumour cells during neoplastic transformation. This finding indicates the metanephric origin of the renal parenchyma. In surgical pathology the possibility of very rare co-expression of cytokeratin and vimentin IF within tumour cells should be considered, particularly in the differential diagnosis of clear cell carcinomas.Dedicated to Prof. Dr. K. Goerttler on the occasion of his 60th birthday     

Distribution of intermediate filament proteins in normal and diseased human glomeruli.

The distribution of intermediate filament proteins (vimentin, desmin, and cytokeratin) was studied by means of immunofluorescence in the normal human and rat glomerulus and in pathologic human glomeruli. Antifibronectin antibodies were used as mesangial markers. In normal human glomeruli, vimentin antibodies stained endothelial cells, podocytes, and mesangial cells; desmin antibodies, surprisingly, stained podocytes. In normal rat glomeruli, the pattern of vimentin staining was the same as in humans, but desmin antibodies stained both mesangial cells and podocytes. In human and rat glomeruli cytokeratin staining was confined to segments of Bowman's capsule. In human pathologic glomeruli, vimentin and desmin antibodies stained the structures that were positive in normal glomeruli, giving a characteristic pattern for each pathologic condition examined. These results are compatible with the mesenchymal origin of podocytes and mesangial cells and suggest that both cells have smooth muscle-like phenotypic features. Mesangial cells may have slightly different differentiation paths in humans and rats, leading to a distinct expression of intermediate filament proteins.     

Cellular origin and differentiation of renal carcinomas. A fluorescence microscopic study with kidney-specific antibodies, antiintermediate filament antibodies, and lectins

Frozen sections of human renal carcinomas were studied in indirect immunofluorescence using antibodies against intermediate filaments of cytokeratin, desmin and vimentin type, and against proximal tubular brush border and distal tubular Tamm-Horsfall glycoprotein antigens, as well as with fluorochrome-labeled lectins in an attempt to study the origin and stage of differentiation of renal carcinomas. Eighty per cent of the renal carcinomas expressed the brush border antigens, whereas the Tamm-Horsfall glycoprotein could not be found. Antibodies against epidermal cytokeratins reacted only with collecting ducts in normal kidney, whereas antibodies against cytokeratins of Madin-Darby canine kidney epithelial cell line also reacted with glomerular and tubular epithelium. In 93% of the carcinomas tumor cells showed reactivity with both types of antikeratin antibodies. Vimentin, the cytoskeletal protein of mesenchymal cells, was present in the carcinoma cells of 53% of the tumors, although it was not present in normal tubular epithelium. Moreover, vimentin was expressed together with cytokeratin in the carcinoma cells in 57% of the keratin-positive samples as judged by double immunostaining, whereas the muscle type of intermediate filament protein, desmin, was not seen in the malignant cells. Binding sites for Lotus tetragonolobus agglutinin and soybean agglutinin, normally present in the cells of proximal tubules, were lacking or only faintly detectable in the neoplastic cells. Dolichos biflorus agglutinin, normally present in collecting ducts, was not detected in the tumors. The results show that most renal carcinomas express cytokeratin antigens as a sign of their epithelial origin and also show characteristics of proximal tubular cells. On the other hand, the results indicate that lectin-binding sites typical for normal differentiated tubular cells are profoundly modified in renal carcinomas. Ulex europaeus agglutinin did not bind to the malignant cells but decorated the endothelial cells of the tumors.     

Intermediate filament proteins and actin isoforms as markers for soft tissue tumor differentiation and origin. I. Smooth muscle tumors.

A series of 3 benign and 10 malignant smooth muscle (SM) neoplasms and of 2 malignant fibrous histiocytomas was examined by light microscopy, transmission electron microscopy, two-dimensional gel electrophoresis (2D-GE) and indirect immunofluorescence, using polyclonal monospecific or monoclonal antibodies to desmin, vimentin, cytokeratin, alpha-SM and alpha-sarcomeric (alpha-SR) actins. Benign neoplasms displayed typical light-microscopic features of SM, whereas leiomyosarcomas demonstrated variations in their histologic pattern. In 6 sarcomas, light microscopy suggested a SM differentiation, whereas in the other 4, a predominant nondistinctive spindle-cell pattern was observed. By transmission electron microscopy, all 13 neoplasms showed the minimal essential features of SM differentiation. Immunofluorescence disclosed heterogeneity of cytoskeletal protein expression: 5 neoplasms (3 benign and 2 malignant well-differentiated) expressed desmin, vimentin, and alpha-SM-actin; 2 malignant neoplasms expressed desmin and vimentin; 1 malignant neoplasm expressed desmin, vimentin and alpha-SR actin; 1 malignant neoplasm expressed vimentin and alpha-SR actin; and 4 malignant neoplasms expressed vimentin alone. By 2D-GE, 3 benign and 4 malignant SM neoplasms expressed alpha, beta, and gamma actins, and the remaining expressed only beta and gamma actins. The presence of alpha-SM actin in all benign neoplasms and in 2 well-differentiated leiomyosarcomas suggests that this actin isoform reflects a high degree of cellular differentiation. In 2 leiomyosarcomas, alpha-SR actin was detected by immunofluorescence, which suggested a skeletal muscle differentiation of these neoplasms. This study supports the assumption that leiomyosarcomas represent a heterogeneous group of neoplasms and furnishes new criteria for their characterization.     

Immunopathology of adrenal and renal cortical tumors. Coordinated change in antigen expression is associated with neoplastic conversion in the adrenal cortex.

A series of adrenal cortical adenomas (ACA) and carcinomas (ACC), as well as normal adrenal cortex have been studied by a panel of 11 antibodies to characterize antigenic changes that may distinguish these morphologically similar entities. Normal adrenal cortex and ACA express low-molecular weight cytokeratin intermediate filaments. However, none of the six primary or seven metastatic ACCs were found to express detectable levels of cytokeratins. In contrast, vimentin was seen in all ACCs studied and was heterogeneously expressed by ACAs. However, its expression was usually confined to stromal elements of the normal adrenal cortex. We conclude that adrenal cortical cells undergo characteristic changes in intermediate filament expression during the process of neoplastic conversion and malignant transformation. Undetectable expression of cytokeratins and strong expression of vimentin is associated with malignant adrenal cortical lesions. In addition, we examined the antigenic phenotype of a series of primary renal cell carcinomas (RCC). Renal cell carcinomas express cytokeratins, while ACCs do not. The majority of primary RCCs express Lewis blood group isoantigens (most commonly Lewis X), while ACAs and ACCs do not. The panel of antibodies described here may help to distinguish morphologically similar lesions of like histogenesis (ACAs vs. ACCs) and lesions of different histogenesis (adrenal vs. renal) on the basis of their composite antigenic phenotypes.     

Immunocytochemical typification of mesothelial cells in effusions: In vivo and in vitro models

We have performed immunocytochemical, immunoelectron microscopy. Western blot, and culture techniques using monoclonal antibodies against cytokeratin, vimentin, and desmin on 17 benign and 20 malignant effusions of pleural and ascitic origin. Triple coexpression of these three antigens was observed in benign reactive mesothelial cells as well as in one case of mesothelioma. All metastatic adenocarcinoma cells were consistently negative to desmin and positive to cytokeratin and vimentin. Present results were helpful to distinguish reactive and malignant mesothelioma from metastatic carcinoma cells in effusions. © 1994 Wiley-Liss, Inc.     

The expression of cytokeratin in hepatic stellate cells of the cod

In the current study, we examined the cytoskeletal architecture of cod hepatic stellate cells. We found that the cod hepatic stellate cells contain abundant cytoplasmic filaments. Deep-etch electron microscopy showed that the major component of the cytoplasmic filaments was intermediate filaments, although microtubules and microfilaments were also found in the cytoplasmic filament bundles. Immunoelectron microscopy revealed the presence of beta-tubulin, alpha-smooth muscle actin, smooth muscle type myosin, desmin and cytokeratin but not vimentin or glial fibrillar acidic protein. These results demonstrate that the cytoplasmic filaments of cod hepatic stellate cells are composed of desmin and cytokeratin intermediate filaments, acto-myosin complexes and microtubules, suggesting that the cod hepatic stellate cells have both contractile and structural functions. The expression of cytokeratin in cod hepatic stellate cells indicates that they serve for mechanical support in the extremely soft liver tissues of cods with their abundant lipids.     

Human lung tumours may coexpress different classes of intermediate filaments

Ninety four pulmonary neoplasms were examined immunocytochemically with two or three different monoclonal antibodies against the intermediate filament proteins cytokeratin, neurofilament, vimentin, and desmin. In normal tissues these have a different and non-overlapping distribution, and it is generally believed that tumours maintain the same pattern of expression as the tissues from which they arise. In this report, however, the coexpression of at least two (and less commonly three or four) different intermediate filaments was seen in 40% (37 of 94) of the cases of lung cancer. These results, especially if confirmed in other common types of human malignancy, have considerable implications for the use of anti-intermediate filament antibodies in diagnostic pathology.     

Expression of intermediate filament proteins in thyroid gland and thyroid tumors

The presence of intermediate filament proteins of cytokeratin/prekeratin type and vimentin type was evaluated in non-neoplastic thyroid glands and in different types of thyroid neoplasms. Follicular epithelium of both normal and goitrous thyroids showed a strong reaction with anticytokeratin antibodies that widely cross-react with various simple epithelia. On the other hand, in normal thyroid, there were only occasionally (in one of 12 cases) solitary cells reacting with antibodies to epidermal prekeratin. In nodular goiters, such cells were often seen (eight of 18), especially among the lining cells of cysts, and in chronic thyroiditis in all (12 of 12) cases. Only the stromal cells and intraluminal macrophages reacted with antibodies to vimentin. Neoplastic cells of papillary carcinomas showed a positive staining reaction both with antibodies to cytokeratins and to epidermal prekeratin. Follicular carcinoma cells, although positive for cytokeratins, could generally not be stained with antibodies to epidermal prekeratin. Medullary carcinoma cells also showed cytokeratin positivity and, only occasionally, positivity for epidermal prekeratin. Anaplastic carcinomas were also reactive with antibodies to cytokeratin but, for the most part, were negative for epidermal prekeratin. Interestingly, some neoplastic cells of all types of thyroid carcinomas also appeared to contain vimentin, as shown with both polyclonal and monoclonal antivimentin antibodies. In contrast to carcinomas, the intermediate filaments of thyroid sarcomas and lymphomas were only of vimentin type. Furthermore, it was found that the papillary structures in benign goiters were only reactive with cytokeratin antibodies and lacked, in contrast to papillary carcinomas, epidermal prekeratin-like immunoreactivity. Hence, the analysis of intermediate filament proteins of thyroid tumors can be utilized to differentiate between papillary and follicular carcinomas and between benign and malignant papillary lesions as well as between anaplastic thyroid carcinomas and sarcomas or lymphomas.