Rhabdoid predisposition syndrome
Early-onset, multifocal disease and familial cases strongly support the possibility of a rhabdoid predisposition syndrome. This has been confirmed by the presence of constitutional mutations of SMARCB1 in rare familial cases and in a subset of patients with apparently sporadic rhabdoid tumors. In a cohort of 74 rhabdoid tumors, 60% of the tumors occurring before age 6 months were linked to the presence of a germline mutation. However, in this same series, tumors that occurred after age 2 years were also found to be associated with germline mutations (7 of 35 cases). Germline analysis is suggested for all individuals with rhabdoid tumors, whatever their ages. Genetic counseling is recommended given the low-but-actual risk of familial recurrence. In cases of mutations, parental screening should be considered, although such screening carries a low probability of positivity. Prenatal diagnosis is feasible and should be considered.
Recommendations for surveillance in patients with germline SMARCB1 mutations have been developed based on the epidemiology and clinical course of rhabdoid tumors. These recommendations were developed by a group of pediatric cancer genetic experts (including oncologists, radiologists, and geneticists). They have not been formally studied to confirm the benefit of screening patients with germline SMARCB1 mutations. The aggressive natural history of the disease, apparently high penetrance, and well-defined age of onset for CNS atypical teratoid/rhabdoid tumor suggest that screening could prove beneficial. Given the potential survival benefit of surgically resectable disease, it is postulated that early detection might improve overall survival. From birth to age 1 year, it is suggested that patients have thorough physical and neurologic examinations, as well as head ultrasounds monthly to assess for the development of a CNS tumor. It is suggested that patients undergo abdominal ultrasounds with focus on the kidneys every 2 to 3 months to assess for renal lesions. From age 1 year to approximately age 4 years, after which the risk of developing a new rhabdoid tumor rapidly declines, it is suggested that brain and spine magnetic resonance imaging (MRI) and abdominal ultrasound be performed every 6 months.
Congenital Mesoblastic Nephroma
Mesoblastic nephroma comprises about 5% of childhood kidney tumors. It is the most common kidney tumor found in infants younger than 3 months. The median age of diagnosis is 1 to 2 months and more than 90% of cases appear within the first year of life. Twice as many males are diagnosed as females. The diagnosis should be questioned when applied to individuals older than 2 years. When diagnosed in the first 7 months of life, the 5-year event-free survival (EFS) rate is 94% and the overall survival (OS) rate is 96%.
Grossly, mesoblastic nephromas appear as solitary, unilateral masses indistinguishable from nephroblastoma. Microscopically, they consist of spindled mesenchymal cells. They can be divided into two major types: classic and cellular. Classic mesoblastic nephroma is often diagnosed by prenatal ultrasound or within 3 months after birth and closely resembles infantile fibromatosis. Infantile fibrosarcoma and cellular mesoblastic nephroma contain the same t(12;15)(p13;q25) chromosomal translocation suggestive of a potential linkage. The risk for recurrence within mesoblastic nephroma is closely associated with the presence of a cellular component and with stage.