Rare SMARCB1 deficient tumors, more commonly occurring in adult patients, include synovial sarcomas, epithelioid malignant peripheral nerve sheath tumors, myoepithelial carcinomas, extraskeletal myxoid chondrosarcomas, chordomas, gastrointestinal stromal tumors (GIST) and ossifying fibromyxoid tumors. The gene discussed is SMARCB1; the disease is gastrointestinal stromal tumor.