As demonstrated by Kastelein et al. using three-dimensional whole-tumor imaging, hypoxic conditions in PM are due to poor perfusion of the microvasculature.22 Consistent with their findings, our clinical samples also showed more frequent and prominent CAIX-positive regions, reflecting hypoxia in PM relative to the primary tumor and lymphatic and liver metastases, and CD36 expression was upregulated, consistent with CAIX expression. This evidence concerns the gene CA9 and neoplasm.