De novo dedifferentiated SDH-deficient gastrointestinal stromal tumor with MDM2 amplification: case report and literature review

The dedifferentiation of the gastrointestinal stromal tumors (GISTs) has been reported in a small number cases, usually under pressure tyrosine kinase inhibitor (TKI) treatment. Herein, we described de novo dedifferentiated GIST with SDH deficiency 32-year-old Chinese woman. tumor was located on lesser curvature gastric antrum, measuring 4.1x9.1 cm 2 . Microscopically, composed distinct morphological populations, mild epithelioid cells arranged multinodular growth pattern and hyperchromatic spindle fascicular or sheet-like architecture. two zones showed different immunophenotypes. former proved to be an positive expression for C-KIT, DOG-1, CD34, latter expressed CKpan P53, but negative CD34. However, SDHB staining both areas. Genetically, next-generation sequencing (NGS) analysis SDHC mutation (p.S48*) components MDM2 amplification only cell area. lesion diagnosed as SDH-deficient epithelial dedifferentiation. We proposed that P53 associated gene alteration other alternative escape mechanisms KIT-independent signaling pathways might play role