The spectrum of pulmonary infections in cancer patients.

The lung is a common site of infection in patients with cancer. The spectrum of pulmonary infection depends on the underlying immunologic deficit or deficits. In neutropenic patients, gram-negative bacterial infections predominate early, whereas fungal infections (Aspergillus, Zygomycetes, Fusarium species) are common if neutropenia persists. In patients with impaired cellular immunity, viral infections (cytomegalovirus, other herpes viruses) predominate and may coexist with bacterial (Legionella, Nocardia), mycobacterial, and fungal (Aspergillus, Histoplasma, etc.) infections. Pneumocystis carinii pneumonia is also common in this setting. Infections caused by Streptococcus pneumoniae and Haemophilus influenzae are the primary bacterial infections encountered in patients with impaired humoral immunity. In patients with primary or metastatic pulmonary neoplasms, postobstructive pneumonitis, lung abscess, and occasionally empyema of mixed bacterial etiology (Staphylococcus species, gram-negative bacilli, anaerobes) are frequent. Patients with brain tumors and head and neck cancer develop aspiration pneumonitis, which is usually caused by organisms living in the oropharynx and upper airways. Several immunologic deficits might be present in the same patient, making such a patient susceptible to a wide variety of opportunistic pathogens.