IMMUNOHISTOCHEMISTRY, ACTIN (SMOOTH MUSCLE ACTIN)

What this test checks

Detects smooth muscle actin protein, which is expressed in smooth muscle cells, myofibroblasts, and myoepithelial cells. Used to classify tumours with smooth muscle or myofibroblastic differentiation.

Why do people get this test?

SMA helps identify specific tumour types including leiomyomas, leiomyosarcomas, and some breast lesions — ensuring accurate classification and appropriate treatment.

When you should consider this test

• When investigating a tumour suspected to arise from smooth muscle
• When classifying soft tissue tumours
• When evaluating breast lesions for myoepithelial cell presence

How to prepare

No preparation needed — performed on biopsy or surgical tissue.