These sections are from the lung of a pigeon breeder who presented with dyspnea and cough. The left photo shows a chronic granulomatous interstitial inflammation with giant cells. In the right photo giant cells are present in the submucosa of a bronchus which also shows a mild lymphocytic infiltrate.
Hypersensitivity pneumonitis, aka allergic alveolitis, results from an immunological reaction to inhaled antigens. Examples include farmer’s lung due to inhalation of Thermoactinomyces in moldy hay, bird-fancier’s or pigeon-breeder’s lung due to inhaled avian proteins, bagassosis from inhalation of T. vulgaris in moldy sugar cane, et al.
From the slide collection of the late Dr. Charles Kuhn