A 46-year-old man has had a slowly enlarging nodule on his trunk for the past 10 months. On examination, the 5-cm lesion is in the right anterior axillary line at the level of the nipple and has a central ulcerated plaque. The lesion is widely excised and on microscopic examination is composed of dense spindle cells in a storiform pattern that invades the dermal adipose tissue. The lesion recurs within a year, and the man is treated with a tyrosine kinase inhibitor. Molecular analysis of the lesion is most likely to show activation with overexpression of which of the following genes?