Inflammatory Breast Cancer: Yet Another Risk of the Obesity Epidemic?

Extract

Two of the most perplexing problems in breast cancer, inflammatory breast cancer (IBC) and obesity, are linked in the report by Schairer and colleagues in this issue of the Journal ( 1 ). In particular, these results show a striking fourfold increased risk of IBC in obese women compared with normal weight individuals (body mass index [BMI] < 25kg/m ² ).

IBC constitutes approximately 1–6% of all breast cancers ( 2 , 3 ), which makes studies of its risk factors somewhat difficult. IBC has an aggressive clinical course, with a 5-year disease-free survival of only 34% ( 4 ). Although IBC has been recognized as a separate entity ( 5 ), we know surprisingly little about both its etiology and pathophysiology.

IBC is a clinical diagnosis made when at least a third of the breast is involved with erythema or peau d’orange ( 6 ). In spite of its name, inflammatory cells are not characteristically seen. A pathologic finding associated with IBC is dermal lymphatic invasion by tumor cells; however, this finding is not necessary for the diagnosis. Some studies have noted an increase in microvessel density in IBC, suggesting that these tumors are angiogenic ( 7 ). Gene expression profiling studies have shown that although all subtypes of IBC exist, basal and human epidermal growth factor receptor 2 overexpressed types are the most common ( 8–12 ).