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?

Dermatofibrosarcoma protuberans is the malignant counterpart of dermatofibroma. The PDGFB gene is juxtaposed with the promoter region of COL1A1, leading to the up-regulation of a growth-promoting factor. Imatinib mesylate can be employed to inhibit the PDGF receptor tyrosine kinase to control lesions that are recurrent or metastatic. FGFR3 mutations are more characteristic of seborrheic keratoses. KIT mutations are found in mast cell proliferation. Basal cell carcinomas have PTCH1 mutations. TSC1 mutations are found in tuberous sclerosis, with skin manifestations, including ash-leaf patches, shagreen patches, subungual fibromas, and angiofibromas.