Histopathology

Since cytologic findings may be inconclusive at
times, tumor biopsy is often needed.

Cytokeratin staining helps to confirm invasion and
to distinguish MM from sarcoma or melanoma.

MM is characterized by the presence of staining for
EMA, calretinin, WT1, mesothelin, and the absence
of staining for antigens such as CEA, tumor
glycoproteins B72, MOC-31.

Electron microscopy also helps to distinguish MM
from adenocarcinoma or to differentiate
desmoplastic or sarcomatoid mesothelioma from
fibrous pleuritis.