Inflammatory breast cancer (IBC) is an aggressive form of locally advanced breast cancer with high metastatic potential. Most patients have lymph node involvement at the time of diagnosis and 1/3 of the patients have distant metastases. In a previous study, we demonstrated that IBC is a distinct form of breast cancer in comparison with non-IBC. The aim of this study was to investigate the presence of the different molecular subtypes in our data set of 16 IBC and 18 non-IBC specimen. Therefore, we selected an 'intrinsic gene set' of 144 genes, present on our cDNA chips and common to the 'intrinsic gene set' described by Sorlie et al. [PNAS, 2003]. This set of genes was tested for performance in the Norway/Stanford data set by unsupervised hierarchical clustering. Expression centroids were then calculated for the core members of each of the five subclasses in the Norway/Stanford data set and used to classify our own specimens by calculating Spearman correlations between each sample and each centroid. We identified the same cell-of-origin subtypes in IBC as those already described in non-IBC. The classification was in good agreement with immunohistochemical data for estrogen receptor protein expression and cytokeratin 5/6 protein expression. Confirmation was done by an alternative unsupervised hierarchical clustering method. The robustness of this classification was assessed by an unsupervised hierarchical clustering with an alternative gene set of 141 genes related to the cell-of-origin subtypes, selected using a discriminating score and iterative random permutation testing. The contribution of the different cell-of-origin subtypes to the IBC phenotype was investigated by principal component analysis. Generally, the combined ErbB2-overexpressing and basal-like cluster was more expressed in IBC compared to non-IBC, whereas the combined luminal A, luminal B and normal-like cluster was more pronounced in non-IBC compared to IBC. The presence of the same molecular cell-of-origin subtypes in IBC as in non-IBC does not exclude the specific molecular nature of IBC, since gene lists that characterize IBC and non-IBC are entirely different from gene lists that define the different cell-of-origin subtypes, as evidenced by principal component analysis.

Purpose: Lymph node (LN) lymphangiogenesis has recently been shown to be important in the premetastatic niche of sentinel LNs. To study its role in the further metastatic spread of human breast cancer, we investigated the association of angiogenesis and lymphangiogenesis in sentinel LN metastases with the presence of nonsentinel LN metastases in breast cancer patients with a positive sentinel LN. Experimental Design: Angiogenesis and lymphangiogenesisöquantified as endothelial cell proliferation fraction (ECP%) and lymphatic ECP fraction (LECP%)öwere assessed in sentinel LN metastases of 65 T 1 /T 2 patients with breast cancer using CD34/Ki67 and D2-40/Ki67 immunohistochemical double stains. Correlations were analyzed between nonsentinel LN status, LECP%, and other clinicopathologic variables (number of involved sentinel LNs, size of the primary tumor and LN metastasis, presence of lymphovascular invasion in the primary tumor, and of extracapsular growth in the sentinel LN metastasis). Results: Thirty seven out of 65 patients (56.9%) had at least one involved nonsentinel LN. Size of the sentinel LN metastasis (P = 0.001), lymphovascular invasion (P = 0.02), extracapsular growth (P = 0.02), and LECP% (P = 0.01) were correlated with a positive nonsentinel LN status. The multivariate logistic regression model retained high LECP% (odds ratios = 4.2, P = 0.01) and the presence of extracapsular growth (odds ratios = 3.38, P = 0.04) as independently associated with the presence of nonsentinel LN metastases. Conclusions: Increased sentinel LN metastasis lymphangiogenesis is associated with metastatic involvement of nonsentinel axillary LNs. These are the first data sustaining the hypothesis that sentinel LN lymphangiogenesis is involved in further metastatic spread of human breast cancer. Primary breast tumors can metastasize in two different ways:tumor cells can leave the primary tumor and spread by the lymphatic or by the hematogenous route leading to the formation of locoregional lymph node (LN) and distant metastases, respectively (1). In the lymphatic pathway, the sentinel LN is the first metastatic station and a sentinel LN free of carcinoma has a very high negative predictive value for further lymphatic dissemination in patients with breast cancer.Axillary LN dissection and associated morbidity could therefore be avoided in 65% to 70% of patients with breast cancer (2). Even in cases of metastatic involvement of the sentinel LN, metastases in further axillary LNs will only be present in 30% to 60% of the patients. Several authors studied the features of sentinel LN metastasis and of the primary tumor that can predict axillary nonsentinel LN involvement. The size of the sentinel LN metastasis has emerged as a most powerful independent predictor in several studies (3 -15). Furthermore, the number of involved sentinel LNs (3,4,7,10,11,16), extracapsular growth of the sentinel LN metastasis (3,6,15), the size of the primary tumor (7,9,10,13,14), and the presence of lymphovascular invasion (4,7,9,14,15) have ...