Fig. 6. Volcano plots for peak intensity comparison of the epithelial and stromal components of fibroadenoma and low-grade phyllodes tumor, respectively, sampled by matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS).

Each black point on the plot is an individual m/z. The x-axis of the plot shows the fold change in peak intensity where data points on the left indicate higher peak intensity in fibroadenoma and data points on the right indicate higher peak intensity in phyllodes tumor. The areas between the two vertical black dotted lines indicated less than minimal change. The y-axis shows the p-value resulting from an unpaired t-test of fibroadenoma vs. low-grade phyllodes tumor samples with the horizontal red dotted line indicating a significant threshold of 0.05 in p-value. The volcano plot shows wider distribution of the data points in the stromal component (b) than in the epithelial component (a) indicating more difference in the stromal component between the two entities. However, the data points are below the p < 0.05 threshold.