Table 6.

Differential diagnoses of PPMS.

Diagnosis	Morphology	IHC	Common Genetic Alterations
Salivary gland myoepithelial tumors	Strands/nests/ductular structures of epithelial/myoepithelial cells; and chondromyxoid/hyalinised stroma	Epithelial cells: EMA, cytokeratins; Myoepithelial cells: GFAP, S100, SOX10, p40, p63, and SMA	PLAG1 or HMGA2 fusions
Angiomatoid fibrous histiocytoma	Syncytial/whorling pattern (classic AFH); reticular/lace-like pattern (myxoid AFH); uniform histiocytoid cells; blood-filled pseudocysts; and inflammatory/lymphocytic reaction (lymph node-like)	Desmin, EMA, and ALK	EWSR1-ATF1 or EWSR1-CREB1
Extraskeletal myxoid chondrosarcoma	Multinodular; lace-like/reticular pattern; round-spindle monomorphic cells with eosinophilic cytoplasm; and myxoid stroma	Non-specific; S100 (focal)	NR4A3-EWSR1/TAF15/TCF12/TFG