The common differential diagnoses are:
Mesothelioma with glandular component from adenocarcinoma. Many antibodies have been applied to this problem, none of them totally specific.
Mesothelioma with squamous differentiation from squamous cell carcinoma. Much less information has been published on the immunohistochemistry of this differential.
Sarcomatous mesothelioma from sarcoma and other spindle cell tumours: see the immunohistochemistry of the differential diagnosis of spindle cell tumours of the pleura.