Crush artifact from forceps including (i) compression of alveolar parenchyma that gives a false impression of interstitial fibrosis or cellular infiltrates, (ii) compression of alveolar parenchyma creating rounded spaces that may be confused with fungus or lipid vacuoles, (iii) compression of bronchial lymphocytes or other cells that may be misinterpreted as small-cell carcinoma, and (iv) compression of large bronchial vessels or other components of the bronchial wall that may give a false impression of interstitial fibrosis.

Intra-alveolar hemorrhage caused by the biopsy procedure may give a false impression of intra-alveolar hemorrhage from disease.

Materials from surgical gloves (starch or talc), cotton fibers from pads, or sutures may mimic organisms or exposures to exogenous dusts or other materials; these may be highlighted on special stains or polarized light (cotton fibers are “Gomori methenamine-silver [GMS] positive”).

Ordinary dust, dirt, and fibers that may settle on a slide in the laboratory will often be birefringent on polarized light and should not be mistaken for foreign material present in the patient’s lungs.