The American journal of surgical pathology
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Am. J. Surg. Pathol. · Feb 2009
Case ReportsRhabdomyosarcomatous differentiation in gastrointestinal stromal tumors after tyrosine kinase inhibitor therapy: a novel form of tumor progression.
Approximately 80% of advanced metastatic gastrointestinal stromal tumors (GISTs) respond to treatment with the tyrosine kinase inhibitor (TKI) imatinib mesylate. However, the majority of patients suffer disease progression at a median of 2 years due to drug resistance. In general, progressing GISTs retain their typical morphology. ⋯ It is associated with loss of KIT expression, but retention of the receptor tyrosine kinase mutation of the precursor GIST. The rhabdomyoblastic differentiation can represent a diagnostic pitfall. The molecular mechanisms for this form of TKI-resistant clonal evolution remain to be determined.