Special Stains to Differentiate LAM cells from Normal Smooth Muscle Cells

Smooth Muscle Actin

Smooth muscle actin stains normal smooth muscle as well as LAM cells.

From the known location of normal smooth muscle in the bronchial wall, identify:

Normal subepithelial smooth muscle

Smooth muscle around 3 examples of dilated bronchial veins.

LAM cells around an alveolated space. (Note a remaining alveolar wall in the upper portion of the space.)

By excluding the normal smooth muscle, one can see the distribution of all LAM cells.


Stain for HMB45

An antibody to HMB45 reacts with a gp100 protein that is present in melanosome-like granules of some, but not all, LAM cells. This antibody also stains cells of angiomyolipomas.


Outline the normal unstained subepithelial smooth muscle cells.

Outline the cluster of LAM cells, only some of which stain positively for HMB45.



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Bronchial vein. These become dilated as pulmonary veins become obstructed by the proliferating LAM cells.



























Normal smooth muscle of bronchial wall




























Normal unstained smooth muscle of bronchial wall




























Cluster of LAM cells, some of which stain for HMB45






























LAM cells