Table 1.

Mature adipocytes vs. cancer-associated adipocytes

	Mature adipocytes	CAAs
Definition	Adipose tissue occupies 56% of the non-lactating breast tissue and 35% of lactating breast tissue. Adipocytes that constitute breast tissue are WAT, with lipid-storage and endocrine functions.	Adipocytes at the invasive front of breast tumor exhibit a modified phenotype, a loss of lipid content, a decrease in late adipocyte differentiation markers and overexpression of inflammatory cytokines and proteases.
Location	Mature adipocytes encapsulate around the mammary gland; Adipocytes are separated with epithelial cells by the basement membrane.	Locate at the invasive front of breast tumor; Adjacent to BC cells.
Morphology	Normal cell size; Round shape; Large unilocular lipid droplets.	Smaller cell size; Irregular shape with smaller size; Smaller and dispersed lipid droplets.
Function	Maintain normal breast morphology; With endocrine functions and maintain the energy balance; Normally expression of adipokines, including leptin, adiponectin, IL-6, CCL2, CCL5 and other cytokines.	Aberrantly expressional secretion of adipokines, including leptin, adiponectin, IL-6, CCL2, CCL5 and other cytokines.
Impact on breast cancer	The promoting effect of adipocytes on BC is far less compared with CAAs; The risk of BC might increase under the condition of obesity.	The interaction between CAAs and BC cells may directly affect their morphology and function; CAAs could promote BC cell proliferation, viability, migration and invasion in vitro, and could enhance tumor growth and metastasis in vivo xenograft studies in a paracrine manner.

Abbreviations: WAT, white adipocytes; BC, breast cancer; IL-6, interleukin 6; CCL2, chemokine ligand 2; CCL5, chemokine ligand 5; CAAs, cancer-associated adipocytes