Table 1.

Test results for the differential diagnosis of LGMFS.

Feature	Description	Comparison with Other Tumors
EM	· Spindle or stellate tumor cells · Abundant microfilaments, microtubules, and collagen fibers · Reflects fibroblastic properties and active protein synthesis	Distinguish LGMFS from fibrosarcoma, leiomyosarcoma, malignant fibrous histiocytoma, synovial sarcoma, and fibromatosis
CD34	· Uncommon in LGMFS	· Strong positivity in angiosarcoma
S100	· Negative in LGMFS	· Positive in MPNST and schwannomas
α-SMA	· Focally positive in LGMFS	· Widespread SMA positivity in leiomyosarcoma
STAT6 and H3 K27Me3	· Both absent in LGMFS	· Present in SFT
p16 and CDK4	· Both absent in LGMFS	· Present in DFSP
FISH	· No PDGFB translocation or COL1A1::PDGFB fusion · No MDM2 amplification	· PDGFB translocation or COL1A1::PDGFB fusion in DFSP · MDM2 amplification in liposarcomas

This table summarizes key features for the differential diagnosis of LGMFS, highlighting electron microscopy findings, immunohistochemical markers, and genetic differences compared to other soft tissue tumors. LGMFS, Low-grade myofibroblastic sarcoma; EM, Electron microscopy; FISH, Fluorescence in situ hybridization; SFT, Solitary fibrous tumor; DFSP, Dermatofibrosarcoma protuberans.