Background: Traditional Chinese Medicine Constitution(TCMC)refers to the relatively stable physical and psychological characteristics of the human body.It has been suggested that unbalanced TCMCs largely contribute to individual susceptibility to various diseases.This study attempted to investigate the distribution of the TCMCs of healthy Chinese women and breast cancer women in Hong Kong,with the objective of evaluating the efficacy of TCMC as potential predictors for the occurrence of breast cancer among Chinese women.Methods: A retrospective,cross-sectional and case-control matched design was utilized in this study.Chinese women with breast cancer and healthy Chinese women were recruited and then assessed using the Traditional Chinese Medicine Physical Constitution Scale for their TCMC types.Social-demographic information and related risk factors for breast cancer were collected through structured questionnaires.Multiple factor analysis was used to explore the association of unbalanced TCMC types with breast cancer.Results: 305 healthy women and 305 breast cancer patients were involved in this study.Compared with healthy women,the proportion of four unbalanced constitutions(Qidepressed,Qi-deficiency,Wetness-heat and Yin-deficiency constitutions)in breast cancer women was significantly higher than those in healthy women(p values less than 0.05).Stepwise logistic regression analysis indicated that only Qi-depressed constitution was significantly positively correlated with breast cancer(OR=3.21,CI 1.49-6.92).In addition,the correlation increased when Qi-depressed constitution combined with Wetness-heat constitution(OR=4.82,CI 1.83-12.71)or Blood-stasis constitution(OR=3.27,CI 1.31-8.16).Moreover,the combination of Wetness-heat constitution and Blood-stasis constitution may also closely related to breast cancer(OR=2.88,CI 1.02-8.17)Conclusion: Qi-depressed constitution could act as an independent risk factor for breast cancer.Wetness-heat constitution and Blood-stasis constitution may also play the role in the occurrence of breast cancer when combined with Qi-depressed constitution or with each other.This indicates that the unbalanced TCMC types could point to the variability in individual susceptibilities to breast cancer,suggesting the feasibility of Chinese constitutional analysis as potential approach in identifying the susceptible population to breast cancer and the corresponding prevention of breast cancer.