Background Many researches suggested that obesity increased the risk of breast cancer,but the mechanism wascurrently unknown.Adipocytokines might mediate the relationship.Our study was aimed to investigate the relationshipbetween serum levels of resistin,adiponectin and leptin and the onset,invasion and metastasis of breast cancer.Methods Blood samples were collected from 80 newly diagnosed,histologically confirmed breast cancer patients and50 age-matched healthy controls.Serum levels of resistin,adiponectin and leptin were determined by enzyme-linkedimmunosorbent assays(ELISA);fasting blood glucose(FBG),lipids,body mass index(BMI),and waist circumference(WC)were assayed simultaneously.Results Serum levels of adiponectin((8.60±2.92)mg/L vs(10.37±2.81)mg/L,P=0.001)and HDL-c were significantlydecreased in breast cancer patients in comparison to controls.Serum levels of resistin((26.35±5.36)μg/L vs(23.32±4.75)μg/L,P=0.000),leptin((1.35±0.42)μg/L vs(1.0±0.39)μg/L,P=0.003),FBG and triglyceride(TG)in breast cancerpatients were increased in contrast to controls,respectively.However,we did not find the significant difference of theserum levels of resistin,adiponectin and leptin between premenopausal breast cancer patients and healthy controls(P=0.091,0.109 and 0.084,respectively).The serum levels of resistin,adiponectin and leptin were significantly differentbetween patients with lymph node metastasis(LNM)and those without LNM(P=0.001,0.000 and 0.006,respectively).The stepwise regression analysis indicated that the tumor size had the close correlation with leptin(R~2=0.414,P=0.000)and FBG(R~2=0.602,P=0.000).Logistic regression analysis showed that reduced serum levels of adiponectin(OR:0.805;95%CI:0.704-0.921;P=0.001),HDL(OR:0.087;95%CI:0.011-0.691,P=0.021),elevated leptin(OR:2.235;95%C1:1.898-4.526;P=0.004)and resistin(OR:1.335;95%CI:1.114-2.354;P=0.012)increased the risk for breastcancer;Reduced serum levels of adiponectin(OR:0.742;95%CI:0.504-0.921;P=0.003)and elevated leptin(OR:2.134;95%CI:1.725-3.921;P= 0.001)were associated with lymph node metastasis of breast cancer.Conclusions The decreased serum adiponectin levels and increased serum resistin and leptin levels are risk factors ofbreast cancer.The low serum adiponectin levels and high serum leptin levels are independent risk factors for metastasisof cancer.The association between obesity and breast cancer risk might be explained by adipocytokines. Background Many researches suggested that obesity increased the risk of breast cancer, but the mechanism was currently unknown. Adipocytokines might mediate the relationship. Our study was aimed to investigate the relationship of serum levels of resistin, adiponectin and leptin and the onset, invasion and metastasis of breast cancer. Methods Blood samples were collected from 80 newly diagnosed, histologically confirmed breast cancer patients and 50 age-matched healthy controls. Serum levels of resistin, adiponectin and leptin were determined by enzyme- linked immunosorbent assays (ELISA); fasting blood glucose Results Serum levels of adiponectin (8.60 ± 2.92) mg / L vs. (10.37 ± 2.81) mg / L, P = 0.001) and HDL- c were significantly increased in breast cancer patients in comparison to controls. Serum levels of resistin ((26.35 ± 5.36) μg / L vs (23.32 ± 4.75) μg / L, P = 0.000) vs (1.0 ± 0.39) μg / L, P = 0.003), FBG and triglyceride (TG) in breast cancer patients were increased in contrast to controls, respectively. However, we did not find the significant difference of the serum levels of resistin, adiponectin and leptin between premenopausal breast cancer patients and healthy controls (P = 0.091, 0.109 and 0.084 , respectively). The serum levels of resistin, adiponectin and leptin were significantly different between patients with lymph node metastasis (LNM) and those without LNM (P = 0.001, 0.000 and 0.006, respectively). The stepwise regression analysis indicated that the tumor size had The close correlation with leptin (R 2 = 0.414, P = 0.000) and FBG (R 2 = 0.602, P = 0.000) .Logistic regression analysis showed that reduced serum levels of adiponectin (OR: 0.805; 95% CI: 0.704 (OR: 0.087; 95% CI: 0.011-0.691, P = 0.021), elevated leptin (OR: 2.235; 95% CI: 1.898-4.526; (OR: 0.742; 95% CI: 0.504-0.921; P = 0.003) and elevatedLeptin (OR: 2.134; 95% CI: 1.725-3.921; P = 0.001) were associated with lymph node metastasis of breast cancer. Conclusions The decreased serum adiponectin levels and increased serum resistin and leptin levels are risk factors ofbreast cancer.The low serum adiponectin levels and high serum leptin levels are independent risk factors for metastasis of cancer. The association between obesity and breast cancer risk might be explained by adipocytokines.