Tumeurs malignes à « cellules rondes » non lymphoïdes des tissus mous de l'enfant et de l'adolescent

Soft tissue non lymphoid malignant round cell tumors observed in children and adolescents are rare and are very different from adult tumors. They are often undifferentiated and distinctive key morphologic features are often lacking, but, on the other hand, specific recurrent genetic alterations, mostly translocations, are distinctive. Immunohistochemical features are also important for the diagnosis, and there is sometimes a strong correlation between the presence or the absence of an immunoreactivity for a specific protein and the presence of a specific genetic alteration. Finally, careful morphologic histological examination and immunohistochemical features will lead to a diagnosis which will be often confirmed by cytogenetics (translocations) or molecular techniques (fusion transcripts, deletion, mutation).