- Discovered in 1986 (J Cell Biol 1986;103:2787)
- Antibodies to alpha smooth muscle actin do not detect the other actin isoforms
- Also called smooth muscle actin, SMA; clone 1A4 or sm-1
- No apparent deficiency in intestinal pseudoobstruction (J Clin Pathol 2004;57:1168)
- May predict aggressive behavior in cutaneous basal cell carcinoma (Hum Pathol 2010;41:1128) and pancreatic ductal adenocarcinoma (Pancreas 2010 May 7 [Epub ahead of print])
- Predictor of good prognosis in lung adenocarcinoma (Mod Pathol 2009;22:776)
- A potential prognostic factor in idiopathic pulmonary fibrosis (Clinics (Sao Paulo) 2012;67:1039)
- Membranous or cytoplasmic staining
- Identify smooth muscle cells and myofibroblasts in normal, reactive (Am J Respir Cell Mol Biol 1999;20:582) or neoplastic tissue (Am J Dermatopathol 2006;28:105)
- Identify myoepithelial cells in normal, neoplastic or diseased breast, salivary glands or sweat glands; may be helpful to rule out invasion; may be particularly important in cytology specimens (Anticancer Res 2003;23:4175)
- Identify pericytes to correlate with hematogenous metastasis and prognosis (Oncology 2005;69:159)
- Help distinguish pleuropulmonary desmoid tumors (SMA+) from solitary fibrous tumor (SMA-, Arch Pathol Lab Med 2006;130:1503)
- Note: in breast papillary lesions, p63 is more sensitive and specific because smooth muscle actin also stains stromal cells (J Clin Pathol 2007;60:315)
Images from Pathout server:
Leiomyosarcoma: cervix
Sinonasal hemangiopericytoma
Images from other servers:
Ameloblastic carcinoma
Bladder: PEComa
Bone: glomus tumor
Breast: myoepithelial cells (fig C/G)
Breast: leiomyoma
Colon (left to right): carcinosarcoma; leiomyoma (top); Peutz Jeghers polyp (fig 4)
Colon and small intestine: normal and intestinal pseudoobstruction
Crohn disease: obliterative muscularization
Eye: MFH of conjunctiva (top left)
Heart: fetus with heart block
Heart scar tissue
Inflammatory myofibroblastic tumor (left to right): bone, gallbladder, salivary gland (fig 3b)
Kidney (left to right): atypical epithelioid angiomyolipoma (two images), focal segmental glomerulosclerosis
Leiomyosarcoma (left to right): bladder (fig C), esophagus
Liver: glomangioma (fig 5)
Lung: COPD
Lung: lymphangio-leiomyomatosis
Myofibroblastic sarcoma
(left: smooth muscle actin,
right: calponin)
Myofibroblastic sarcoma
(left: smooth muscle actin,
right MIB-1)
Normal: breast myoepithelial cell disruptions
Normal: breast myoepithelial cells
Normal: decidual stromal cells
Normal: eye choroid and sclera
Normal: liver (fetal)
Placenta accreta (fig 3)
Plexiform fibrohistiocytic tumor
Pleomorphic sarcoma / MFH
Salivary gland duct carcinoma
Salivary gland sialometaplasia in parotid node
Stomach: left-gastric carcinoma-diffuse type (fig A); right-gastric carcinoma-intestinal type (fig A)
Submandibular gland - adenoid cystic carcinoma
Images from Nature.com:
Breast: basal-like carcinoma (fig A)
Breast: cellular fibroadenoma
Breast: adenoid cystic carcinoma
(fig B) vs collagenous spherulosis
(fig G)
Neuroblastoma
Lung: adenocarcinoma, subepithelial myofibroblasts
Liver: epithelioid angiomyolipoma
- Breast myoepithelial cells (most, Breast Cancer Res 2003;5:R151, Proc Natl Acad Sci U S A 1993;90:999)
- Chondrocytes (Folia Biol (Praha) 2006;52:167), choroidal non-vascular smooth muscle cells (J Anat 2005;207:381)
- Decidual stromal cells (Hum Reprod 1999;14:1599), fibroblastic reticulum cells (J Cancer Res Clin Oncol 1981;101:149)
- Glomus coccygeum (Arch Pathol Lab Med 1999;123:905), hepatic stellate cells (Virchows Arch 1997;430:195)
- Myofibroblasts (except alveolar - J Histochem Cytochem 1992;40:1955, and some granulation tissue / scars - Lab Invest 1989;60:275, Int J Legal Med 1992;105:99)
- Osteoblasts (J Orthop Res 2002;20:622)
- Pericytes (J Histochem Cytochem 1989;37:315)
- Salivary glands
- Smooth muscle and vascular smooth muscle (Proc Natl Acad Sci U S A 1981;78:298)
- Sweat glands and tracheobronchial glands (J Histochem Cytochem 1988;36:659)
- Adenoid cystic carcinoma (Arch Pathol Lab Med 1999;123:801)
- Angiomyofibroblastoma (occasionally focal, Hum Pathol 1997;28:1046, J Med Case Rep 2010;4:79)
- Angiomyolipoma (J Egypt Natl Canc Inst 2013;25:125)
- Atypical teratoid / rhabdoid tumor (J Neurosurg 1996;85:56, Brain Tumor Pathol 2008;25:79)
- Breast: intraductal carcinoma (PLoS One 2013;8:e57773)
- Cellular angiofibroma (focal, 41% Mod Pathol 2011;24:82)
- Collagenous spherulosis (Mod Pathol 2006;19:1351)
- COPD: large airways have increased expression of SMA (Respir Res 2011;12:48)
- Endometrial stromal sarcoma (65%, Gynecol Oncol 2004;92:71)
- Endometriosis-stroma (Pathol Int 2003;53:371, Pathol Int 2013;63:429)
- Epithelial-myoepithelial carcinoma (Am J Surg Pathol 2007;31:44)
- Epithelioid sarcoma-proximal type (33%, Am J Surg Pathol 1997;21:130, 15%, Mod Pathol 2001;14:655)
- Fibromatosis (56%, Am J Surg Pathol 2002;26:1296)
- Fibroblastic reticulum cell tumor (Am J Surg Pathol 1998;22:1048)
- Gastric carcinoma stromal cells (J Clin Pathol 2002;55:741)
- GIST (45%, Am J Surg Pathol 2002;26:1296, Am J Pathol 1990;136:771)
- Glomus tumor (Hum Pathol 1999;30:1259, Am J Pathol 1990;136:771)
- Granulosa cell tumors of ovary-adult (variable, Mod Pathol 1995;8:25)
- Hemangiopericytoma (Am J Surg Pathol 2003;27:737)
- Kidney-focal segmental glomerulosclerosis (Braz J Med Biol Res 2001;34:985)
- Inflammatory myofibroblastic tumor (Ann Diagn Pathol 2001;5:335, Am J Surg Pathol 1992;16:896, Turk J Gastroenterol 2012;23:399)
- Leiomyoma
- Leiomyosarcoma (Int J Gynecol Pathol 2011;30:236, Anticancer Res 2005;25:1559)
- Liposarcoma (focal in 45%, Am J Surg Pathol 2004;28:1257)
- Maligant fibrous histiocytoma (J Clin Pathol 2003;56:666)
- Melanoma-desmoplastic and non-desmoplastic sarcomatoid,(Am J Dermatopathol 1999;21:537, J Clin Pathol 1996;49:950)
- Mesothelioma-sarcomatoid (60%, Histopathology 2003;42:270)
- Myoepithelioma (Hum Pathol 2004;35:14)
- Myofibroblastic sarcoma (Chin Med J (Engl) 2007;120:363, Int J Oral Sci 2012;4:170)
- Nodular fasciitis (Ann Diagn Pathol 2002;6:94)
- Ossifying fibromyxoid tumor (some, J Laryngol Otol 1993;107:75; 6%, Am J Surg Pathol 2011;35:1615)
- Pancreatic stellate cells post-obstruction (J Surg Res 2003;114:6)
- Plexiform fibrohistiocytic tumor (Histopathology 1991;19:503)
- Plexiform fibromyxoma (Am J Surg Pathol 2009;33:1624)
- Pulmonary lymphangioleiomyomatosis (J Clin Pathol 1993;46:479, Tohoku J Exp Med 2003;199:119)
- Renal mixed epithelial and stromal tumor (Arch Pathol Lab Med 2006;130:80, Beijing Da Xue Xue Bao 2008;40:415)
- Rhabdomyoma (focal / rare, Hum Pathol 1993;24:754, Hum Pathol 1993;24:608)
- Rhabdomyosarcoma, alveolar (Korean J Ophthalmol 2006;20:70)
- Rhabdomyosarcoma embryonal (botryoid type, Pediatr Dev Pathol 2005;8:427)
- Spindle cell carcinoma (Am J Surg Pathol 2001;25:1009)
- Synovial sarcoma (25%, Mod Pathol 2007;20:760)
- Cardiac muscle (positive during development, J Cell Sci 2007;120:229)
- Skeletal muscle (J Cell Biol 1985;100:807)
Disease:
- Carcinomas (usually)
- Myofibroblastoma (occasionally focally positive, Pathology 2005;37:144, Am J Surg Pathol 2001;25:1022)
- Schwannoma, solitary fibrous tumor (Arch Pathol Lab Med 2006;130:1503)
