I Sir i : The classification of spindle cell tumours with monomorphic morphology and lacking a clear immunophenotype remains challenging. The identification of the I TFG i - I RET i chimeric tyrosine kinase gene in this group of spindle cell tumours coexpressing CD34 and S100 adds I RET i to a list of oncogenic tyrosine kinase genes, i.e. I RAF1 i , I BRAF i , and I NTRK1 i / I 2 i , in the pathogenesis of this tumour type. Spindle cell tumors with RET gene fusions exhibit a morphologic spectrum akin to tumors with NTRK gene fusions. [Extracted from the article]