Desmin

Desmin is one of the intermediate filament proteins in the cytoplasm of the muscle cells. Immunohistochemistry (IHC) detection for desmin antigen shows cytoplasmic staining pattern with perinuclear dot-like positivity in certain tumors. Desmin is a very good immunomarker for muscle differentiation. Desmin IHC can be used for the identification of smooth muscle tumors (desmin+) from gastrointestinal stromal tumor (only 3 – 5% desmin+). Desmin IHC is very useful in differentiating rhabdomyosarcoma (embyonal/pleomorphic/spindle cell/sclerosing type, desmin+) from undifferentiated pleomorphic sarcoma (desmin-), from extrarenal rhabdoid tumor (desmin-), from proliferative fasciitis / myositis (desmin-) , and from infantile fibrosarcoma (desmin-) . Desmin IHC identifies benign rhabdomyoma (desmin+) from granular cell tumor (desmin-) and from crystal storing histiocytosis (desmin-). Desmin IHC can be important in distinguishing myofibroblastoma (desmin+) from solitary fibrous tumor (desmin-, STAT6 +). Approximately 85% of cases of reactive mesothelial proliferation are immunoreactive to Desmin IHC while only 10% of case with malignant mesothelioma are positive for Desmin.