In 2019, Croce recommended that uterine spindle cell sarcomas could be divided into three categories: NTRK fusion group, COL1A1–PDGFB fusion group, and a group that was tentatively classified as malignant peripheral nerve sheath tumor as positively stained with S100 and contained neither of the molecular abnormalities above (10), a category that excluded leiomyosarcoma (LMS) and high-grade endometrial stromal sarcoma (HGESS). The gene discussed is COL1A1; the disease is endometrioid stromal sarcoma.