Cancer surveillance represents the most delicate and controversial aspect of the clinical management of patients with BWSp. The (epi)genotype-phenotype correlation studies allowed us to stratify the oncological risk with respect to the different molecular subgroups. For the majority of patients, those affected by IC2-LoM, the tumor risk is low (about 2%) and mostly encompasses hepatoblastoma or rhabdomyosarcoma. On the opposite, the risk is relevant in patients with UPD(11)pat (about 15%) and these patients develop any kind of tumor seen in BWSp, mainly Wilms tumor (WT) and hepatoblastoma, but also adrenal carcinoma and pheochromocytoma. The highest risk is seen in patients with IC1-GoM and approaches 25%, almost exclusively for WT
[18][19].
The cornerstones of surveillance in BWSp are abdominal ultrasound (US) for early detection of WT
[20] and the serum alpha-fetoprotein assay
[21][22][23] used for early diagnosis of hepatoblastoma. The US can detect also hepatoblastoma at advanced stages with respect to alpha-fetoprotein
[24][25], as well as other rarer abdominal neoplasms. The US up to 8 years of age and alpha-fetoprotein assay up to 4 years of age are repeated quarterly based on tumor growth data
[26]. There is a currently unanimous consensus on performing quarterly ultrasound (US) WT screening up to the eighth year of age in patients with IC1-GoM, UPD(11)pat and negative molecular tests
[26]. The position of experts on US screening in patients with IC2-LoM and on screening for hepatoblastoma by means of the alpha-fetoprotein assay, on the other hand, appears varied
[26][27]. In many European countries, the IC2-LoM group is not screened as it has almost no risk for WT and alpha-fetoprotein screening is not adopted given the overall low-risk of hepatoblastoma (less than 5%)
[26]. On the other hand, in the USA, adopting a lower risk threshold (~1%) the IC2-LoM group is screened and the alpha-fetoprotein assay screening is suggested
[28]. However, epidemiology suggests that most tumors in patients with IC2-LoM and hepatoblastoma cases occur within the first 2 years of life, therefore, we adopt the US in IC2-LoM and alphafetoprotein assay every 3 months up to 24–30 months of age for all patients
[29]. A rare epigenetic subtype of BWSp, androgenetic chimerism, is characterized by severe features and very high cancer risk and needs a more frequent and intense screening protocol that can be extended to young adulthood
[30].
It is common that children with WT are diagnosed within the BWSp secondarily to cancer diagnosis
[32]. Moreover, it has been recently demonstrated that up to one-third of children with WT or hepatoblastoma have a 11p15.5 epimutation detectable in the blood
[33] and suggested that this testing might be included among those by a sequencing-based approach to screen for a cancer predisposition in children with such tumors
[33].