Spindle cell squamous carcinoma: ultrastructural observations

Two spindle cell carcinomas of the skin and one of the breast have been studied by electron microscopy. In one tumour the spindle cells were of purely mesenchymal type and in the other two the spindle cells exhibited both mesenchymal and epithelial features within the same cells. The significance of the findings in relation to the histogenesis of the spindle cells is discussed, with special reference to the possible alternative roles of mesenchymal metaplasia of the epithelial component and spontaneous cell fusion between carcinoma cells and stromal cells.