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Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 26 March 2012, update in progress
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● 53 kDa intermediate filament first described in 1976 (Proc Natl Acad Sci USA 1976;73:4344), present near the Z line in sarcomeres, present in cardiac, smooth and striated muscle (Wikipedia)
● Expressed before actin in myoblasts; variable expression in myofibroblasts


Molecular architecture of myocyte

Uses by pathologists

● Common stain used in panels for mesenchymal markers
● Confirms myogenic origin of tissue / tumors
● Helps differentiate smooth muscle tumors (desmin+) from GIST (c-kit+, almost always desmin-)
● In serous effusion, more common in reactive mesothelial cells (84%) than mesothelioma (8%) or carcinoma (2%, Am J Surg Pathol 2001;25:1405)

Micro images

Adrenal gland-perivascular epithelioid cell tumor (fig F) is negative

Breast-myofibroblastoma (inset)

Breast-spindle cell lipoma: spindle cells are desmin negative, breast lobules serve as internal positive control


Heart-rhabdomyosarcoma (right is embryonal subtype)

Hepatorenal embryonal rhabdomyosarcoma-desmin (fig4a), myogenin (4b)

Kidney-angiomyolipoma, smooth muscle predominant


Kidney-mixed epithelial stromal tumor (fig 2C)

Nasal cavity-angioleiomyoma

Pancreas-desmoplastic small round cell tumor

Skin-angiomatoid fibrous histiocytoma

Soft tissue-embryonal rhabdomyosarcoma: left to right - cross striations, rhabdoid cells, spindle cells

Small bowel-obliterative muscularization of the submucosa

Testis-spindle cell variant of embryonal rhabdomyosarcoma


Vulva-aggressive angiomyxoma

Positive staining - normal

● Cervix-decidual reaction, endometrium (focal), fallopian tube stroma, liver-stellate cells
● Mesothelial cells (reactive), myoblasts, myofibroblasts (variable), myometrium, smooth muscle cells

Positive staining - disease

● Adenosarcoma (cervix, prostate, stomach), aggressive angiomyxoma, alveolar soft parts sarcoma (cervix)
● Anaplastic sarcoma-kidney (usually), angioleiomyoma (Hum Pathol 2007;38:645)
● Angiomatoid fibrous histiocytoma (Mod Pathol 2011;24:1560), angiomyofibroblastoma, angiomyolipoma (smooth muscle cells)
● Atypical fibroxanthoma of skin (30%), atypical polypoid adenomyoma of uterus (variable)
● Benign stromal spindle cell tumors (breast)
● Chondrosarcoma-dedifferentiated
● Desmoplastic small round cell tumor (dot-like perinuclear pattern)
● Endometrial stromal sarcoma (50%), endometriosis (associated with desmin+ skeletal muscle regeneration, Am J Surg Pathol 2010;34:10), epithelioid sarcoma (proximal type has variable staining)
● Fibroblastic reticulum cell tumor, fibroepithelial polyp, fibromatosis (usually negative, but may be focal), fibrous hamartoma of infancy (spindle cell areas), fibrous histiocytoma of skin-variable
● Giant cell tumor of tendon sheath-localized type, granulosa cell tumor (variable)
● Hemangiopericytoma (20% in CNS)
● Inflammatory myofibroblastic tumor (variable, Hum Pathol 2008;39:846; epithelioid tumors are usually positive, Am J Surg Pathol 2011;35:135), ischemic fasciitis
● Leiomyoma (Am J Surg Pathol 2001;25:455) and leiomyosarcoma (staining associated with more differentiated tumors, Hum Pathol 2010;41:663)
● Low grade myofibroblastic sarcoma (variable), lymphangioleiomyomatosis, lymphangiomyoma
● Malignant fibrous histiocytoma, malignant mixed Mullerian tumor (cervix-sarcomatous component), medullomyoblastoma, mesenchymal hamartoma
● Mixed epithelial and stromal tumor of kidney (stroma), mycobacterial spindle cell pseudotumor in lymph nodes
● Myofibroblastoma (variable, Hum Pathol 2012;43:243), myofibrosarcoma, myogenic sarcoma, myoid gonadal stromal tumor (Hum Pathol 2012;43:144)
● Neuroblastoma, neuromuscular hamartoma of soft tissue
● Ossifying fibromyxoid tumor (38%, Am J Surg Pathol 2011;35:1615), osteosarcoma (variable)
● Paratesticular fibrous pseudotumor (31%, Am J Surg Pathol 2010;34:569), perivascular epithelioid cell tumors (sclerosing PEComa has diffuse staining, abdominopelvic sarcoma and tumors of falciform ligament / ligamentum teres are negative, other sites are predominantly negative)
● Phyllodes tumor of breast (stroma), PNET (variable), prostatic stromal hyperplasia with atypia (moderate staining, Arch Pathol Lab Med 2008;132:1729)
● Pseudoangiomatous stromal hyperplasia (PASH) of breast (variable), pseudosarcomatous fibroepithelial stromal polyp (cervix, vagina)
● Reactive nodular fibrous pseudotumor (variable), rhabdomyoma, rhabdomyosarcoma (in more differentiated cells)
● Sclerosing stromal tumor (ovary), smooth muscle tumor of pleura, spindle cell carcinoma (variable)
● Spindle cell epithelioma of vagina, stromal sarcoma of prostate (variable), superficial cervicovaginal myofibroblastoma
● Uterine tumors resembling ovarian sex cord tumor (Am J Surg Pathol 2010;34:1749)

Negative staining

● Angiofibroma (positive in 11%, Am J Surg Pathol 2012;36:500)
● Calcifying fibrous tumor (Am J Surg Pathol 2010;34:271), carcinomas (usually), chondromyxoid fibroma, chondrosarcoma-mesenchymal
● Choriocarcinoma, clear cell sarcoma
● Dermatofibrosarcoma protuberans, desmoplastic fibroblastoma
● Ectomesenchymal chondromyxoid tumor, elastofibroma
● Fibroma, fibrosarcoma, follicular dendritic cell sarcoma
● Gastrointestinal stromal tumor (epithelioid tumors may have focal staining), GANT
● Giant cell fibroblastoma, glomus coccygeum, granular cell tumor
● Hemosiderotic fibrohistiocytic lipomatous lesion
● Inflammatory fibroid polyp, interdigitating dendritic cell tumor, intranodal palisaded myofibroblastoma
● Histiocytic sarcoma
● Lipoma (pleomorphic, spindle cell), liposarcoma (but dedifferentiated tumors may be desmin+, Am J Surg Pathol 2010;34:844), lipomatous hemangiopericytoma
● Low grade fibromyxoid sarcoma, lymphoma
● Mesothelioma (Mod Pathol 2012 Jan 6 [Epub ahead of print]), metanephric adenoma / adenofibroma of kidney
● Myoepithelioma, myofibroma, myopericytoma (rarely focal staining, Am J Surg Pathol 2009;33:1666), mxyoma
● Neural tumors (chordoid glioma, neuroblastoma, neurofibroma, perineurioma, schwannoma)
● Nodular fasciitis, nuchal fibrocartilaginous pseudotumor, nuchal type fibroma
● Osteosarcoma
● Pancreatic serous cystadenoma, pigmented villonodular synovitis, plexiform fibromyxoma (Am J Surg Pathol 2009;33:1624)
● Post-operative spindle cell nodule (bladder), proliferative fasciitis / myositis, pseudomyogenic hemangioendothelioma (Am J Surg Pathol 2011;35:190), pseudosarcomatous fibromyxoid tumor of prostate
● Rhabdoid tumor of heart
● Sialadenoma papilliferum, solitary fibrous tumor
● Superficial acral fibromyxoma / digital fibromyxoma (rare focal staining, Am J Surg Pathol 2012 Feb 24 [Epub ahead of print]), synovial sarcoma
● Vascular tumors (angiosarcoma, glomangioma, glomus tumor, hemangiopericytoma outside CNS, Kaposi's sarcoma)
● Warthin’s tumor

End of Stains > Desmin

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