Recent advances in the molecular diagnosis of paediatric soft tissue sarcomas

Sarcomas comprise a significant portion of solid tumours diagnosed in children. As they commonly are composed of primitive round or spindled cells, morphologic diagnosis can be difficult, and ancillary studies are often necessary. In recent years, progress has been made in understanding the cytogenetic and molecular changes underlying many of these tumours, and molecular techniques have emerged from strictly being research tools to becoming standard diagnostic tests. Paediatric sarcomas fall into two categories: those with characteristic underlying translocations, and those without. Translocation associated paediatric sarcomas include, but are not limited to alveolar rhabdomyosarcoma, Ewing's family of tumours, desmoplastic small round cell sarcoma, synovial sarcoma, infantile fibrosarcoma, clear cell sarcoma of soft tissue, and low-grade fibromyxoid sarcoma. Sarcomas without translocations tend to be more pleomorphic in appearance, and include embryonal rhabdomyosarcoma, malignant rhabdoid tumour and epithelioid sarcoma. This review will describe the molecular and immunohistochemical methods most applicable in diagnosing these soft tissue malignancies.