Image Description
This is a case of Extranodal Rosai-Dorfman disease (RDD) involving lung. The pulmonary architecture is distorted by massive thickening of alveolar septa due to dense fibrosis, proliferation of S-100 positive histiocytes, and lymphoplasmacytic infiltrate.
Involvement of lung in RDD is extremely rare. The list of entities in the differential diagnosis is long and includes: inflammatory myofibroblastic tumor, pulmonary hyalinizing granuloma, Langerhans' cell histiocytosis, Erdheim-Chester disease, infections (granulomatous, actinomycosis, botryomycosis), chronic aspiration, granular cell tumor, histiocytic malignancies, malakoplakia, focal eosinophilic pneumonia without eosinophils, histiocyte accumulation in areas of scarring, and pneumoconioses.
Involvement of lung in RDD is extremely rare. The list of entities in the differential diagnosis is long and includes: inflammatory myofibroblastic tumor, pulmonary hyalinizing granuloma, Langerhans' cell histiocytosis, Erdheim-Chester disease, infections (granulomatous, actinomycosis, botryomycosis), chronic aspiration, granular cell tumor, histiocytic malignancies, malakoplakia, focal eosinophilic pneumonia without eosinophils, histiocyte accumulation in areas of scarring, and pneumoconioses.