The very low likelihood to have relevant heterogeneity among the about 500 tumor cells that are typically present in a 0.6 mm TMA spot is perfectly reflected by the markedly lower rate of heterogeneous PTEN IHC loss (2%) in the current study as compared to other TMA cohorts with 3-4 tumor cores sampled from each case [13, 25]. This evidence concerns the gene PTEN and neoplasm.