The two basic components of cancer therapy have long been chemotherapy and radiation therapy. Both these modalities, especially chemotherapy, were based on the cytotoxic effect they exerted on cancer cells. Their cytotoxicity, of course, carried over to both rapidly dividing normal cells and nonmalignant host cells. The most commonly affected cells were those of the lymphatic and hematopoietic systems. Destruction of these cells, most notably the neutrophil, could leave the patient with less cancer, but it would also leave the patient with less immunity, and therefore, more susceptibility to infection. Death in these patients was frequently due to infection rather than malignancy.

Oncology has now progressed to the point that survival for extended periods of time can take place with control as opposed to eradication of the cancer. Although a patient is less immunocompromised with receptor blockers, monoclonal antibodies, tyrosine kinase inhibitors, antiangiogenic therapy, and therapies yet to be discovered, there is still immune suppression and a larger window of time for infections to develop. There is also a much larger number of patients for whom infection, not cancer, becomes the life-threatening event.

The seminal laboratory finding that is most often associated with these infections is decreased numbers of neutrophils. Also, most of these infections will occur when the neutrophil count is at its lowest. Improvement conversely occurs when the neutrophil count begins to return to normal. Prophylactic antibiotics are often used when the neutrophil count is drastically reduced.

Leukemia and lymphoma are more capable of interfering with neutrophil function and numbers. As a result, both of them are more likely to present with skin infections at the onset.