Concurrent myeloid sarcoma, atypical teratoid/rhabdoid tumor, and hypereosinophilia in an infant with a germline SMARCB1 mutation.

We report a 1-year-old female child presenting with hypereosinophilia who was found to have concurrent myeloid sarcoma and a central nervous system (CNS) atypical teratoid/rhabdoid tumor (AT/RT). She was later found to have a germline mutation in SMARCB1. Concurrent hematologic malignancy and CNS AT/RT have not previously been described in the context of a SMARCB1 loss-of-function germline mutation.