Histologic changes: This nodule (A) surrounds a still-recognizable bronchiole that is filled with inflammatory cells and histiocytes. Bronchiolar epithelium is flattened. The entire wall and adjacent alveoli are infiltrated by the histiocytes and inflammatory cells. Note that the smooth muscle is also invaded and being destroyed by the process (remnants of muscle at arrows). This bronchiolocentric process accounts for the airflow obstruction that has occurred in this patient.
This section (B) shows a pulmonary artery surrounded and narrowed by the infiltrate (3 arrows indicate its outer border). If many arteries are involved, pulmonary hypertension, which is potentially reversible, may result. Also note the histiocytes with brown pigment (arrowheads mark two) that are mixed with the Langerhans' cells. They are ordinary, phagocytic histiocytes that contain smokers' pigment.
Clinical summaryImage 4
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