Abstract
BACKGROUND: Inflammatory breast cancer (IBC) is an aggressive form of breast cancer that on presentation resembles locally advanced breast cancer (LABC). This study identified molecular features of IBC and LABC to investigate pathogenesis. MATERIALS AND METHODS: This study involved 100 IBC cases identified in a national IBC registry and 107 non-IBC LABC cases from the National Cancer Institute's Cooperative Breast Cancer Tissue Resource (CBCTR). Vascular endothelial growth factor D (VEGF-D) and E-cadherin levels and lymphatic vessel density (LVD) measured by podoplanin staining were examined by immunohistochemistry on paraffin-embedded tumor specimens. Intralymphatic tumor emboli (ILTE) were assessed in IBC and non-IBC tumors. IBC cases diagnosed by clinicians but not meeting the case definitions of the American Joint Committee on Cancer (AJCC) or the Surveillance, Epidemiology and End Results (SEER) Program of the National Cancer Institute (NCI)(designated atypical IBC) were compared with AJCC- and/or SEER-defined cases (designated classic IBC). RESULTS: E-cadherin levels were significantly higher in classic IBC cases compared with non-IBC cases (P = .031), whereas compared with classic IBC, patients with non-IBC LABC had significantly higher LVD (P = .0017) and VEGF-D levels (P < .0001). ILTE was marginally greater in classic IBC than in non-IBC (P = .046). The profile of laboratory values in atypical IBC cases more closely resembled those fitting classic IBC than LABC. CONCLUSION: E-cadherin levels, LVD, VEGF-D expression, and to a lesser extent, ILTE differed between classic IBC and non-IBC LABC. The similarity of laboratory results between atypical IBC and classic IBC vs. LABC suggests the need for broadening both the AJCC and SEER case definitions for this disease.