title: Intermediate filament proteins and actin isoforms as markers for soft tissue tumor differentiation and origin. I. Smooth muscle tumors.
abstract: 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.
mesh_terms: D000199:Actins / Q000032:analysis*; D000911:Antibodies, Monoclonal; D002454:Cell Differentiation; D003893:Desmin / Q000032:analysis; D005455:Fluorescent Antibody Technique; D018219:Histiocytoma, Benign Fibrous / Q000473:pathology; D006801:Humans; D007381:Intermediate Filament Proteins / Q000032:analysis*; D007633:Keratins / Q000032:analysis; D007890:Leiomyosarcoma / Q000473:pathology / Q000648:ultrastructure; D008854:Microscopy, Electron; D009130:Muscle, Smooth; D009379:Neoplasms, Muscle Tissue / Q000032:analysis*; D012509:Sarcoma / Q000473:pathology; D014746:Vimentin / Q000032:analysis
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; D003893:Desmin; D007381:Intermediate Filament Proteins; D014746:Vimentin; D007633:Keratins