Leukemias and lymphomas involving the lung were diagnosed by means of exfoliative cytology in 31 specimens from 20 patients. Initial diagnostic categorizations included 29 specimens "positive for malignancy," including two thought to represent 'karcinoma vs. lymphoma, '' and two considered suspicious for lymphoma.
Previous diagnoses of lymphoma (13 patients) and acute myelogenous leukemia (AML) (2 patients) were available. In 5 additional patients, ex foliative respiratory cytology yielded the j r s t diagnosis of hematopoietic malignancy. Cytologic diagnosis included nine large-cell and six small-cell non-Hodgkin 5 lymphomas (NHL), three Hodgkin ' s lymphomas (HD), and two AML. Key cytologic features included markedly pleomorphic and monomorphic cell populations in HD and NHL, respectively, as well as lack of tumor cell cohesion and necrosis in all cases. Cytologically, acute leukemia may be dificult to differentiate from large-cell NHL, and small-cell N H L from reactive/benign small lymphocytes. Blood, scant cellularity, crush artifacts, and apparent molding may affect diagnostic accuracy. Immunocytochemistry in cell block sections of sputa and washings is useful in the diagnostic workup in selected cases. Although involvement of the respiratory system by leukemias and lymphomas is uncommon and not alwayspreceded by a history of malignancy, cytologic diagnosis is usually prompt, reliable, and accurate.