Paediatric soft tissue tumours: from histology to molecular diagnosis

Paediatric sarcomas comprise a diverse group of relatively uncommon neoplasms, with morphological features that range from primitive round cell tumours to fasciculated spindle cell cancers. These histologies frequently overlap and cause diagnostic confusion or uncertainty, so that ancillary testing has become the standard of practice. In previous years, immunohistochemistry and electron microscopy were commonly used, but the genetic revolution has led to the discovery of unique molecular markers that can be detected using routinely fixed and embedded tissues. Detection of characteristic genetic features of paediatric sarcomas has become more readily available and offers advantages over other ancillary tests, so that general pathologists should be familiar with molecular markers and the procedures used to detect them. This brief review outlines the more common types of paediatric sarcomas and describes the morphological and genetic features that facilitate their diagnosis.