Pulmonary involvement by chronic lymphocytic leukemia/small lymphocytic lymphoma is a specific pathologic finding independent of inflammatory infiltration.

Pulmonary infiltrates in patients with chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are usually secondary to infection, but a subset is due to pathologic infiltration of malignant lymphocytes into the lung parenchyma. In cases with both CLL/SLL and inflammatory infiltrates, it is unknown whether the CLL infiltrate represents a nonspecific "passenger effect" secondary to ongoing inflammation or pathologic leukemic pulmonary infiltration (LPI). We reviewed 49 lung biopsies taken from 38 patients with CLL/SLL. LPI was found in 2 of 21 cases (9.5%) with acute inflammation, 0 of 10 cases of chronic inflammation and in 7 of 18 cases (38.8%) without any pathologic findings of acute or chronic inflammation (p = 0.01). These results demonstrate that LPI identified in biopsies with concurrent inflammation is uncommon, and that most inflammatory infiltrates in patients with CLL do not cause "passenger effect" CLL infiltration. Therefore, LPI usually represents a specific pathologic process. We conclude that bronchoscopy with transbronchial biopsy is an effective tool for guiding treatment decisions for symptomatic patients with CLL with pulmonary infiltrates. Moreover, LPI by CLL is not a bystander effect secondary to acute inflammation, but instead represents a distinct pathologic process in a subset of patients.