[Spindle cell carcinomas. Immunohistochemical analysis of 15 cases].

Fifteen spindle cell carcinomas, 9 from the larynx, 4 from skin, 1 from pharynx and 1 from the esophagus were studied with a variety of mesenchymal and epithelial markers: vimentin (VIM), smooth muscle actin (ACT), desmin (DESM), cytokeratin (AE1), polyclonal keratin (Q), and epithelial membrane antigen (EMA). Peroxidase-antiperoxidase and avidin-biotin complex techniques were used. Ten of the lesions were biphasic and the remaining 5 monophasic, showing only the spindle cell component. The spindle cell areas were positive for ACT (14/15), VIM (13/15), DESM (10/15), Q (10/15), AEi (14/15) and EMA (3/15). There were 12 cases in which the spindle cell component was stained with epithelial and mesenchymal markers. Areas of squamous cell carcinoma were positive with the epithelial markers and unstained with the mesenchymal markers. These results support the concept of a bidirectional differentiation in the pathogenesis of these lesions with a "mesenchymal" metaplasia of malignant epithelial cells.