What is the epidemiology of pulmonary Langerhans cell histiocytosis?
Young adult smokers. There is no gender predilection.
What is the classic characterization of the cysts that form in pulmonary Langerhans cell histiocytosis?
Cysts can be irregularly shaped, and adjacent fibrosis can cause the appearance of thick walls. This is in contrast to lymphocytic interstitial pneumonitis (LIP) and lymphangioleiomyomatosis (LAM), which both classically result in thin walled, regular shaped cysts.
H&E stains show large groups of macrophages centered in the small airways, stellate nodules, and cystic change. CD1a immunohistochemistry, which is specific for Langerhans cells, is diffusely positive.
12.5x H&E stain
Sclerotic foci (blue arrow) are surrounded by emphysema (red arrow).
400x HE
Clusters of macrophages are centered in the small airways.
100x CD1a immunohistochemistry
Diffusely positive for Langerhans cells.