HTR2B and breast cancer: The gut microbiota has a direct impact on the synthesis of 5-hydroxytryptamine (5-HT) by colonic enterochromophils in the gastrointestinal tract,87 This process is significant in macrophage M2 polarization.88,89 Furthermore, 5-HT has been found to increase the proliferation rate and decrease the apoptosis rate of breast cancer cells, which can lead to increased aggressiveness.90 Additionally, the receptors 5-hydroxytryptamine receptor 2B (HTR2B) and HTR7 can be considered as macrophage polarization markers, indicating M2 skewed polarization.89