Typical mammary adipose tissue (MAT) cellular composition. (A) Pre-adipocytes, immature precursor of mature adipocytes; (B) white adipocytes, with lipid-storage and endocrine functions, contain single lipid droplet occupies the largest part of the cytoplasm; (C) brown adipocytes, containing several cytoplasmic small fatty droplets and mitochondria, with uncoupling protein 1 (UCP1)-dependent thermoregulatory functions; (D) beige adipocytes, with UCP1-independent thermoregulatory functions; (E) dying adipocytes, form crown-like structures due to macrophage recruitment, causing the release of reactive nitrogen species (RNS) and reactive oxygen species (ROS); (F) cancer-associated adipocytes, with unbalanced production of pro-inflammatory cytokines.