The risk of cancer in children with Noonan Syndrome is around 8 times higher. Since cancer in children is very rare, the risk is still not very great, and the majority of children with Noonan syndrome do not develop cancer. The cancer spectrum lists the following types of cancer (not exhaustive): low-grade glioma (a relatively benign brain tumor), acute leukemia, neuroblastoma, and rhabdomyosarcoma.
Specific mutations in PTPN11 are associated with an increased risk of excess blood formation during the first months of life. This myeloproliferative disorder sometimes progresses in an aggressive manner, and requires treatment. In such cases, it is important to consult experienced pediatric oncologists.
Noonan-syndrome-like CBL syndrome is associated with a high risk of juvenile myelomonocytic leukemia. Even though this is malignant, not everyone who is affected requires treatment, as the clinical progression can be benign. Here as well, it is important to involve an experienced pediatric oncologist.