1. Necker University Hospital, 75015 Paris, France.
2. Department of Pediatrics, Institute Gustave Roussy, 94805 Villejuif, France
3. Orthopedic Surgery Department, Necker University Hospital, 149 rue de Sèvres, 75015 Paris, France
4. Laboratoire d'anatomie et cytologie pathologiques, Institut Universitaire du Cancer de Toulouse- Oncopole, 1 avenue Irène Joliot-Curie. 31059 Toulouse Cedex 9, France