Plexiform fibromyxoma: Review of rare mesenchymal gastric neoplasm and its differential diagnosis

Table 1 Differential diagnoses of plexiform fibromyxoma

Neoplasm	Morphology	Immunohistochemistry	Molecular alteration	Location	Behavior
Plexiform fibromyxoma	Ovoid to spindle	SMA (+), CD10 (+/-), desmin (+/-), caldesmon (+/-), C-KIT (-), DOG-1 (-), S-100 (-), CD34 (-), ALK (-), cytokeratin (usually -)	MALAT1–GLI1, PTHC1 inactivation	Stomach	Benign
GIST	Spindle, epithelioid or mixed	C-KIT (+), DOG-1 (+), S-100 (usually -), CD34 (+), desmin (usually -), cytokeratin (-), SDHB (no loss)	KIT, PDGFRA	Stomach, small intestine, entire GI tract	Benign or malignant
SDH deficient-GIST	Usually epithelioid	C-KIT (+), DOG-1 (+), S-100 (-), CD34 (+), SDHB (loss), desmin (-), cytokeratin (-)	No KIT or PDGFRA mutation	Stomach	Benign or malignant
Smooth muscle tumor	Mostly spindle, rarely epithelioid	Desmin (+), SMA (+), DOG-1 (-), C-KIT (-), S-100 (-), CD34 (-)		Esophagus, colon	Benign or malignant
Nerve sheath tumor	Wavy spindle	GCT: S-100 (+), Schwannoma: S-100 (+); Neurofibroma: CD34 (+), S-100 (+); Perineurioma: EMA (+); MPNST: S-100 (weak +)	NF1, NF2	Esophagus (GCT), stomach (schwannoma)	Benign or malignant
Myxoma	Bland spindle or stellate	Vimentin (+), CD34 (+/-), S-100 (+/-), cytokeratin (-), SMA (-)		Rare in GI tract	Benign
Angiomyxoma	Spindle to stellate	ER (+), PR (+), SMA (+), desmin (+), vimentin (+), CD34 (+/-), C-KIT (-), DOG-1 (-), S-100 (-), cytokeratin (-)	HMGA2 rearrangement	Extremely rare in GI Tract	Benign, locally aggressive
Gastroblastoma	Biphasic with epithelial and spindle	Epithelial cells: AE1:AE3 (+), CK18 (+); Spindle cells: vimentin (+), CD10(+); Both: C-KIT (-), SMA (-), desmin (-), S-100 (-), CD34 (-), CD99 (-), ER (-), p63 (-), calretinin (-), chromogranin (-), synaptophysin (-), TTF-1 (-)	MALAT1–GLI1	Stomach	Malignant
Malignant epithelioid tumor with GLI1 rearrangement	Epithelioid, ovoid, round to spindle	S-100 (+/-), SMA (+/-), cytokeratin (+/-)	MALAT1–GLI1, GLI amplification, GLI1 fusions	Soft tissue, jejunum	Malignant

GIST: Gastrointestinal stromal tumor; SDH: Succinate dehydrogenase; SDHB: Succinate dehydrogenase immunostain; GCT: Granular cell tumor; MPNST: Malignant peripheral nerve sheath tumor; GI: Gastrointestinal.