Tumours of Soft Tissue and Bone, and Other Mesenchymal Tumours

Abstract

Soft-tissue tumours are less common than epithelial or haematolymphoid neoplasms, and consequently they are more likely to pose diagnostic uncertainty. Nevertheless, most soft-tissue lesions are diagnosed with a satisfactory level of confidence on the basis of clinical findings, histology, immunohistochemistry (IHC), and cytogenetic/molecular-genetic studies. However, problem cases, where the cellular differentiation may be difficult to define, are still encountered from time to time (Rampisela and Donner, 2004). Partly, this is due to the limitations of IHC: fibroblastic tumours, for instance, have a poor immunoreactivity towards the commonly used panels of immunostains that most laboratories maintain; α-smooth-muscle actin (SMA) not only stains leiomyosarcoma but also tumours showing myofibroblastic, pericytic, endothelial cell, myoepithelial cell and epithelial differentiation (specifically, in regard to the last group, metaplastic carcinomas). In such circumstances, electron microscopy can contribute diagnostically (Fisher, 2006; Santucci and Franchi, 2008). As in other groups of tumours, an ultrastructural input can be helpful where diagnostic uncertainty is due to conflicting clinical, histological and immunohistochemical findings, and, as always, fine structural data can add to our understanding of the biology of soft-tissue tumours.