LAM Cells vs Smooth Muscle Cells

Image 1

Look at images 1 and 2. Both show lesions composed of cells that stain as smooth muscle.

Compare

Nuclear size

Nuclear hyperchromaticity

Vascularity

Are the muscle bundles discrete or intertwined?

What is the diagnosis of each?

Answers

Image 2

Image 3

vaclam1vaclam2

Besides appearing spindled, LAM cells can also appear rounded (epithelioid) with vacuolated cytoplasm as shown here. This variation in histologic appearance also occurs in angiomyolipomas, in which the perivascular epithelioid cell can show different types of differentiation.

Find two collections of rounded, vacuolated LAM cells around this airway.

 

Besides morphology, immunohistochemical stains can differentiate between the cells of LAM and those of normal smooth muscle.

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Image 1

 

Nuclear size: Nuclei are larger and more irregularly shaped in lesion 2.

Nuclear hyperchromaticity: Nuclei are more hyperchromatic (darkly stained) in lesion 2.

Vascularity: Vascularity is more prominent in lesion 2.

Are the muscle bundles intertwined or discrete? Muscle bundles are discrete in lesion 1 and intertwined in lesion 2.

Image 2

 

 

What is the diagnosis of each?

Image 1 shows a focus of smooth muscle metaplasia around a subpleural focus of honeycombing in usual interstitial pneumonia. It represents a reactive proliferation of smooth muscle cells.

Image 2 shows a clonal proliferation of perivascular epithelioid cells in lymphangioleiomyomatosis.

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Rounded, vacuolated LAM cells

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