Malignant rhabdoid tumor of the bladder and ganglioglioma in a 14 year-old male with a germline 22q11.2 deletion

Malignant rhabdoid tumors (MRTs) are rare pediatric malignancies characterized by clinically aggressive lesions that typically show loss of SMARCB1 expression. We herein describe a case of a malignant rhabdoid tumor of the bladder in a 14-year-old male with an autism spectrum disorder and a de novo 3 Mb germline deletion in chromosome band 22q11.2 that included the SMARCB1 gene. The malignancy developed in the setting of chronic hematuria (>2 years) following the occurrence of two other lesions: a central nervous system ganglioglioma and an intraoral dermoid cyst. MRTs of the bladder are exceedingly rare, and this patient is the oldest child reported with this tumor to date. This case adds to the growing body of literature regarding the recently described, phenotypically diverse, distal 22q11.2 syndrome. Furthermore, this is the first reported case in which an MRT of the bladder appears to have developed from a pre-existing bladder lesion. Finally, this case further supports a rhabdoid tumorigenesis model in which heterozygous loss of SMARCB1 predisposes to initial tumor formation with intact SMARCB1 expression, with subsequent inactivation of the other SMARCB1 allele, which results in transformation into more malignant lesions.