Markers of subtypes in inflammatory breast cancer studied by immunohistochemistry: Prominent expression of P-cadherin

To determine breast cancer subtypes we studied by immunohistochemistry the expression of 12 proteins in a series of 91 Tunisian IBC and 541 non-IBC deposited in tissue microarrays.We considered infiltrating ductal cases only. We found 33.8% of basal cases in IBC vs 15.9% in non-IBC (p < 0.001), 33.3% of ERBB2-overexpressing cases in IBC vs 14.5% in non-IBC (p < 0.001), and 29.3% of luminal cases in IBC vs 59.9% in non-IBC (p < 0.001). The most differentially-expressed protein between IBCs and non-IBCs was P-cadherin. P-cadherin expression was found in 75.9% of all IBC vs 48.2% of all non-IBC (p < 0.001), 95% of IBC vs 69% of non-IBC (p = 0.02) in basal cases, and 82% of IBC vs 43% of non-IBC (p < 0.001) in luminal cases. Logistic regression determined that the most discriminating markers between IBCs and non-IBCs were P-cadherin (OR = 4.9, p = 0.0019) MIB1 (OR = 3.6, p = 0.001), CK14 (OR = 2.7, p = 0.02), and ERBB2 (OR = 2.3, p = 0.06).Tunisian IBCs are characterized by frequent basal and ERBB2 phenotypes. Surprisingly, luminal IBC also express the basal marker P-cadherin. This profile suggests a specificity that needs further investigation.Inflammatory breast cancer (IBC) represents less than 10% of all breast cancers but is the most lethal form of the disease [1]. Evolution of this distinct and aggressive form of locally-advanced breast cancer depends on the type of neo-adjuvant chemotherapy but is overall poor [2]. IBC, classified T4d (stage IIIB) according to the TNM classification of the American Joint Committee of Cancer [5], is generally a rapidly growing tumor associated with cutaneous erythema and edema [2-4]. The inflammatory aspect is associated with highly angiogenic and angio-invasive properties and with the presence of dermal lymphatic emboli [5]. The high metastatic potential of IBCs suggests a high propensity of the tumor cells to migrate.IBCs in Tunisia are characterized by a higher frequency and a higher aggressiveness than in European countries [6