The epidemiology of inflammatory breast cancer.

The epidemiology of inflammatory breast cancer (IBC) has been of great interest to a number of investigators, but epidemiological research has been hampered by the lack of an agreed upon case definition and the relatively small number of patients available to any single investigator or institution. Several features of IBC have become apparent through population-based studies, which, although varying somewhat in case definition, generally agree on some key features of the disease. These include the incidence of the disease, apparently less than 3% of breast cancer cases in the United States, the younger age of onset compared to non-inflammatory breast cancer, the much higher incidence in Black women compared to White, the generally poor outcome of this disease compared to non-inflammatory breast cancer, and the continued increase in reported incidence, particularly as compared with non-inflammatory breast cancer in general and locally advanced breast cancer (LABC) in particular. There is an apparent striking geographic pattern, with a higher percentage of cases reported from North Africa, best documented in Tunisia. The risk factors for developing IBC are suggested by smaller studies with concordant conclusions, and some appear to be different than the risk factors for developing breast cancer in general. For example, obesity appears to be a risk factor for premenopausal IBC but is not for premenopausal non-inflammatory breast cancer. In addition, there is evidence that a young age at first birth predisposes to IBC but is protective against developing non-inflammatory breast cancer. In some malignancies, the use of molecular markers is helpful in defining subgroups that could assist in improving case definition as well as predicting prognosis. The increasing combination of improved epidemiologic and laboratory methods will hopefully accelerate our understanding of this challenging disease.