In a pathological setting, leiomyoma, LMS, HGESS, and undifferentiated uterine sarcoma should be considered as the main differential diagnosis of COL1A1–PDGFB fusion uterine sarcomas, and NTRK fusion uterine sarcoma should be the most challenging one to be differentiated (23–25). This evidence concerns the gene COL1A1 and leiomyoma.