Clusterin, Ptx3 and Pediatric Febrile Neutropenia (CluPPFeN)

-Primary objective : Evaluate serum levels CLU levels during febrile neutropenia in children followed for cancer. -Secondary objective : 1. Evaluate serum levels of CLU at the beginning of non-febrile aplasia and during a possible 2nd febrile peak 2. Evaluate serum PTX3 levels during febrile neutropenia in children followed for cancer 3. Explore the association between CLU, PTX3 and the severity of the aplasia episode 4. Evaluate the association between CLU and PTX3 levels and the type of pathogen found during febrile aplasia 5. Exploration of the diagnostic contribution of CLU and PTX3 in relation to other known parameters of inflammation (including C reactive protein (CRP), procalcitonin (PCT), fibrinogen, interleukin 1 (IL-1), IL-6, IL-10, Tumor Necrosis Factor (TNF-α), CXCL8, IL17) 6. Exploration of genetic polymorphisms predisposing to bacterial and fungal infections (including PTX3 and CLU gene polymorphisms) in the context of febrile aplasia