Breast cancer patients in Iran are relatively young, and the findings presented here suggest that marital status and a positive family history of breast cancer are risk factors for breast cancer in Iran. This is in accordance with other research findings indicating that a positive family history of breast cancer is a strong risk factor for breast cancer at young age , although this has a comparatively small effect on the absolute lifetime incidence of and mortality from breast cancer . However, with regard to the findings from the present study, one may argue that the relatively high proportion of young breast cancer cases in Iran is most likely due a to a young population structure and to a combination of high age at menarche and low age at first pregnancy, which are protective in later life. Evidence from the USA  also suggests that, in some Asian subgroups such as the Vietnamese, women diagnosed with breast cancer tend to be younger than those from other racial or ethnic groups, with half of the diagnoses occurring in women younger than 50 years; this needs further exploration.
The findings presented here show that never married women were at higher risk for breast cancer. In most studies single and nulliparous married women were found to have a similar increased risk for breast cancer as compared with parous women of the same age . Thus, one may argue that marital status by itself is not a determining factor for increased or reduced breast cancer risk, and rather the main protective effect is from early first full-term pregnancy. However, in the present study no association with parity emerged when multivariate analysis was performed. Evidence suggests that there is an interaction between marital status and parity , supporting a 'dual effect' of parity on breast cancer risk with pregnancy. Studies have shown that interactions between age, family history of breast cancer and parity might exist . In addition, studies have reported that nulliparity reduces risk for breast cancer at younger age and elevates risk in the elderly [9, 10].
The lack of significant associations between breast cancer and the other variables studied was unexpected. For example, studies have shown that past oral contraceptive use is associated with a somewhat higher OR among young women or women who have a family history of breast cancer [11, 12]. However, although there were clear patterns in ORs for most variables (Table 1), we suspect that this lack of significant associations may be explained by the limited power of the present study to estimate risk.
Finally, one should be aware of the limitations of the present study, including case and control ascertainment and representation. Although the results cannot be generalized, the findings suggest that the associations between some known risk factors for breast cancer may differ in Iran as compared with Western countries, and that familial breast cancer in young Iranian breast cancer patients deserves further investigation.