Table 3 Differential diagnosis of diffuse malignant mesothelioma
Differential diagnosisImmunohistochemistry that may help
Primary pleural tumours
AngiosarcomaCD34, CD31, FVIIIRA
Epithelioid haemangioendotheliomaCD34, CD31, FVIIIRA
Synovial sarcomaCytokeratins, CD99, bcl-2, cytogenetics
Sarcomas (various)Various depending on type
Localised malignant mesotheliomaNone
Solitary fibrous tumourCD34, bcl-2, CD99
Well-differentiated papillary mesotheliomaNone (needs macroscopic appearance and usually peritoneum)
Adenomatoid tumourNone (needs macroscopic appearance)
Calcifying tumour of the pleuraNone (usually young patient)
Desmoplastic small round cell tumourCytokeratins, desmin, EMA, WT-1, NSE
Thymic tumoursCytokeratins, EMA, occasionally CD5
LymphomaLymphoid markers
Metastatic tumours
SarcomasVarious depending on type
LymphomasLymphoid markers
Malignant melanomaS-100, HMB45, melan-A
Thymic tumoursCytokeratins, EMA, occasionally CD5
Non-neoplastic mimics
Pleural fibrosisRarely cytokeratins
Reactive mesothelial cellsDesmin, EMA, p53