Because of the potential added clinical value in the assessment of the DNA methylation status of GSTP1, we evaluated several widely-used sodium bisulfite conversion-dependent technologies to assess routinely the DNA methylation status of the GSTP1 promoter in primary breast tumors and potentially other cancers (Figure 1): (1) methylation-specific PCR (MSP) [23]; (2) MethyLight [24]; (3) pyrosequencing (PyroMeth) [25]; and (4) MALDI mass-spectrometry (MALDI-MS) [20,26]. Here, GSTP1 is linked to cancer.