Malignant mesothelioma

The common differential diagnoses vary for the diverse patterns seen in mesotheliomas1:


principle differentials




Mesothelioma with glandular component from adenocarcinoma. Many antibodies have been applied to this problem, none of them totally specific.


acinar (glandular)


solid well differentiated

reactive mesothelial proliferation

solid poorly differentiated

large cell carcinoma, lymphoma

clear cell

metastatic renal cell carcinoma, clear cell carcinoma of the lung, clear cell melanoma

Mesothelioma with squamous differentiation

squamous cell carcinoma


squamous cell carcinoma, pseudotumoral deciduosis, anaplastic large cell lymphoma, oxyphilic variant of ovarian clear cell carcinoma, trophoblastic neoplasia

adenoid cystic

metastatic adenoid cystic carcinoma

signet ring cell (lipid rich)

signet ring cell carcinoma

small cell

small cell carcinoma, desmoplastic small round cell tumour, PNET, lymphoma



osteosarcoma and chondrosarcoma


inflammatory processes, lymphoma, Hodgkin lymphoma


fibrous pleuritis

see the immunohistochemistry of the differential diagnosis of spindle cell tumours of the pleura.


carcinosarcoma, biphasic pulmonary blastoma, biphasic synovial sarcoma


pleomorphic carcinoma




The morphological differentiation of benign mesothelial proliferation from diffuse malignant mesothelioma may be very difficult2. Cytokeratins may help by demonstrating mesothelial cells infiltrating fat or skeletal muscle. Various markers of malignancy have ben proposed for both histological and cytological specimens but are of uncertain value.


1 Allen TC . Recognition of histopathologic patterns of diffuse malignant mesothelioma in differential diagnosis of pleural biopsies. Arch Pathol Lab Med 2005; 129:1415-20

2 Cagle PT,Churg A. Differential diagnosis of benign and malignant mesothelial proliferations on pleural biopsies. Arch Pathol Lab Med 2005; 129:1421-7

This page last revised 8.8.06.

©SMUHT/PW Bishop