Therefore, tumor biopsies orsections may not be representative of the whole tumor lesion.39 Moreover, immunohistochemistry of tumor sectionsdoes not allow longitudinal monitoring of the hypoxia biomarker CAIX.Here, we develop mCAIX microSPECT/CT and demonstrate its potentialto evaluate chronic hypoxia in syngeneic mouse tumors and show thatthe presence of CAIX correlates with hypoxia and low infiltrationof immune cells. The gene discussed is CA9; the disease is neoplasm.