Table 8.

Differential diagnoses of mesothelioma.

Diagnosis	Morphology	IHC	Common Genetic Alterations
Clear-cell sarcoma	Nested-fascicular pattern; epithelioid-plump spindle cells with vesicular nuclei and macronucleoli; fibrous septa; and scattered wreath-like multinucleated giant cells	Melanocytic markers (S100, SOX10, Melan-A, HMB45, and MITF)	EWSR1-ATF1/CREB (most often); EWSR1-CREM (rare)
Desmoplastic small round-cell tumor	Sheets/nests/cords of uniform, small round cells; and variable desmoplastic stroma	Desmin (dot-like), keratin, EMA, and WT1 (C-terminus)	EWSR1-WT1
Carcinoma	Sheets/nests/trabecules; round-oval-epithelioid cells with nuclear atypia and variable cytoplasm	Pankeratins, lineage-specific markers (depending on site of origin)	Diverse (depending on site of origin)