HTR4 and osteosarcoma: Analysis of the association between serotonin receptors (HTR1A, HTR1B, HTR1D, HTR1E, HTR1F, HTR2A, HTR2B, HTR2C, HTR4, HTR5A, HTR6, and HTR7) and osteosarcoma prognosis in the TARGET‐Osteosarcoma database revealed that low expression of HTR2B correlated with patient poor outcomes (Figure1A).