Fig. 1

Patient flowchart. Between January 2004 and December 2009, a total of 1056 patients received modified radical mastectomy (MRM) and had pre-operative mammographic breast density (MBD) measured at our institution. Seventy women who received neoadjuvant chemotherapy were excluded. Recurrences were categorized as locoregional (ipsilateral chest wall or axillary, internal mammary, or supraclavicular nodes) or distant metastasis. Each patient with known locoregional recurrence or distant metastasis (n = 121, the case group) were matched to at least one patient without recurrence (the control group) by pathological disease stage, age, and year of diagnosis