EDNRA and neoplasm: We hypothesize that multispectral optoacoustic tomography (MSOT) using an ETAR-specific probe could provide improved insights into the hypoxic characteristics of the tumor microenvironment (TME), either alone or in combination with endogenous markers, and that alterations in ETAR expression may correlate with increased tumor oxygenation serving as an early indicator of response to anti-angiogenic or immune-modulating therapy.