Background: Inflammatory breast cancer (IBC) is a rare form of aggressive breast cancer with no existing identifiers for screening or prevention strategies. Women with triple-negative (TNBC, ER–, PR–, Her2–) non-inflammatory breast cancer are less likely to breastfeed, and we have shown in adjacent normal breast tissue that this tissue has more foci of stem cells compared to non-TNBC cancers. A disproportionately higher percentage of women with IBC have TNBC relative to women with non-IBC. We hypothesized that adjacent normal tissue in TNBC IBC vs. TN non-IBC may also display unique biological features based on epidemiologic characteristics.

Methods: We examined epidemiologic factors by breast cancer receptor subtype in 144 patients diagnosed with IBC in 1991–2011 at MD Anderson Cancer Center. Breast cancer risk factors including parity and breastfeeding were compared between patients with TN and non-TN IBC with chi-square or Wilcoxon rank sum tests. Normal adjacent tissues were stained for stem cell markers CD44+CD49f+CD133/2+ and macrophage marker CD68.

Results: The mean age at diagnosis was 52.3 years (range = 23–80) and 83% of patients were non-Hispanic white, 80% were overweight or obese (BMI >25), and 36% were TN IBC. Patients with TN IBC had significantly lower frequency of breastfeeding compared with non-TN IBC, 28% vs. 55%, (p = 0.01). No differences were found in the frequency of other breast cancer risk factors. All 8 IBC adjacent tissue samples showed a distinct spatial distribution of stem cell staining, not limited to the triple negative patients. Compared with 0/60 non-IBC cases, 0/8 triple negative non-IBC, (p = 0.001 Pearson chi-square). Given the high BMI among IBC patients, we further examined normal tissues for the presence of CD68+ cells distributed individually or as clusters exhibiting a “crown-like” pattern (multiple CD 68+ macrophages found around dead adipocytes), and found that 7 of the 8 IBC adjacent tissues were CD68+. Benign biopsies collected from 2 patients at 10 years before diagnosis displayed similar staining, including both stem cell and CD68 staining. Compared with 12/60 non-IBC adjacent tissues were positive for CD68, with 1/8 TN non-IBC, (p = 0.001 Pearson chi-square).

Conclusion: We describe for the first time a stem-cell staining pattern unique to IBC present in all IBC tissues examined, including pre-cancer biopsies. Tissue samples from additional patients will be examined to further explore the relationship between stem cells and CD68 positivity with IBC subtypes.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-10-01.