Figure 1: Breast carcinoma effusion and primary carcinoma expression arrays. (a): Volcano plot of differentially expressed genes in malignant effusions in comparison to pooled primary tumors ($n=6$). The xaxis indicates the differential expression profiles, plotting the foldinduction ratios in a log2 scale. The yaxis indicates the statistical significance of the difference in expression (Pvalue, ttest) in a log10 scale. Differentially expressed genes ($P<.05$) appear above the horizontal line. Numbers denote upregulated (red) or downregulated (blue) genes in effusions. (b): Gene expression profiling of effusions (blue) and primary breast carcinomas (red) in threedimensional space by Principal Component Analysis using 351 genes that showed significant up or downregulation in effusions in comparison to the pooled primary tumor sample (two different view angles). (c): Gene expression profiling of 11 effusions (blue) and 11 primary carcinomas (red) in threedimensional space by Principal Component Analysis (three different view angles). 
