[Soft tissue sarcomas: update on molecular data]

Soft tissue sarcomas are rare and may be a source of problems for diagnosis and treatment. Four types of genetic disorders can be distinguished: translocations, gene amplifications, mutations and complex genetic imbalances. Detection of these disorders may help in diagnosis and in determining prognosis. Detection of specific translocation is recommended in synovial sarcoma, alveolar rhabdomyosarcoma or PNET diagnosis because of therapeutic consequences; in case of rarer histologic type (low grade fibromyxoid sarcoma, clear cell sarcoma, infantile fibrosarcoma...), it may confirm the diagnosis. In some cases, some translocations have a prognostic value (alveolar rhabdomyosarcoma) whereas it is discussed in others (synovial sarcoma). The techniques used to detect these translocations are very sensitive so it may be used to detect microscopical metastasis (bone marrow metastasis of alveolar rhabdomyosarcoma for example). Detection of MDM2 and CDK4 genes amplifications (FISH or quantitative PCR) may be sometimes useful in well differentiated and dedifferentiated liposarcomas diagnosis. Mutation detection of KIT or PDGFRA may help in GIST diagnosis and type of mutation is predictive of response to treatment. Study of complex genomic imbalances in sarcomas is not used in routine practice but remains useful in research.