Stains
Actin, alpha smooth muscle type

Author: Gina Johnson, M.D. (see Authors page)

Revised: 3 November 2015, last major update November 2013

Copyright: (c) 2003-2015, PathologyOutlines.com, Inc.

PubMed Search: alpha smooth muscle actin[title]
Definition / General
  • Discovered in 1986 (J Cell Biol 1986;103:2787)
  • Antibodies to alpha smooth muscle actin do not detect the other actin isoforms
Terminology
  • Also called smooth muscle actin, SMA; clone 1A4 or sm-1
Clinical Features
Interpretation
  • Membranous or cytoplasmic staining
Uses by Pathologists
Micro Images

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


Positive Staining - Normal
Positive Staining - Disease
Negative Staining
Normal tissue:

Disease: