FLT3 and synovial sarcoma: The inciting activator of SS, especially classic SS, has not been determined, although cases of hematologic malignancy and initiation of granulocyte colony stimulating factors (G-CSF), all-trans retinoic acid (ATRA), and fms-like tyrosine kinase-3 (FLT3) inhibitors offer a glimpse into one mechanism.