Fungal and viral infections remain a significant cause of morbidity and mortality in patients with cancer. Modern management of infections in cancer requires knowledge of the epidemiology, pathogenesis, treatment, and prevention of such infections. Fungal infections range from nosocomial infections with Candida spp to endemic fungi acquired outside the hospital, such as Histoplasma capsulatum. Opportunistic fungi, especially molds, have emerged as a leading cause of death in patients with leukemia or hematopoietic stem cell transplant (HSCT) (1). Viral infections such as varicella zoster virus (VZV), herpes simplex virus (HSV), or cytomegalovirus (CMV), have been associated with increased morbidity and mortality in patients with cancer, including patients with multiple myeloma or chronic lymphocytic leukemia (CLL), and in HSCT recipients (2,3,4,5). Respiratory viruses, such as respiratory syncytial (RSV), adenovirus, and influenza, are increasingly recognized as significant pathogens in patients with cancer, particularly as molecular diagnostic methods improve. In addition, viruses such as novel influenza H1N1, West Nile virus, bocaviruses, and noroviruses have emerged as newly recognized pathogens in patients with cancer.
Fungal infections pose a continuing challenge for oncology patients. Exposure to fungi is common, with exposure typically occurring in the environment. Patients with cancer are susceptible not only to new infection with endemic fungi (such as Histoplasma capsulatum), but also to reactivation of latent infections. Opportunistic molds, such as Fusarium spp, Scedosprorium spp, and Zygomycetes cause devastating disease in hematologic patients. Cases of nosocomial infection due to molds are reported in the setting of hospital construction, leading to routine air sampling and filtration. In contrast, Candida spp are a common component of the patient’s or health-care workers’ endogenous microbial flora. Manifestations of infection may not present until the patient receives chemotherapy or undergoes HSCT.
Diagnosis of invasive fungal infections is problematic as well, despite increased use of fungal biomarkers (6). The skin and lungs are accessible areas for examination and biopsy as they are commonly affected by fungal pathogens. In our institution, a retrospective study of skin biopsies in patients with leukemia suggested that ulcerated or necrotic skin lesions in the context of bacteremia or fungemia were predictive of infection (7). Of note, skin biopsy revealed infection in 39% of all patients undergoing biopsy and 55% of those with severe neutropenia (7). Of patients with biopsy-proven skin infection, 39% of those infections were fungal, led by Candida species (25%), Fusarium (19%), Mucorales (13%), Aspergillus species (9%), Alternaria (6%), and Curvularia (3%) (7).
In the setting of pulmonary nodules, lung biopsy, utilizing open biopsy or computed tomographic (CT)–guided percutaneous biopsy, has also proven useful in diagnosis. Studies of CT-guided biopsy show a yield of approximately 60% for a specific diagnosis (8). In a study at our center of patients with hematologic malignancy, 34% of the specific diagnoses ...