Background: Chronic inflammation predisposes to several malignancies. We previously demonstrated an obesity → inflammation → aromatase axis in breast tissue. As obesity is a risk factor for postmenopausal (PoM) but not premenopausal (PreM) breast cancer (BC), we examined whether menopause and body mass index (BMI) independently impact breast white adipose tissue (WAT) inflammation. Methods: WAT was prospectively collected from patients (pts) from 04/10 – 08/13. WAT inflammation, detected by CD68 immunohistochemistry, was defined by the presence of dead/dying adipocytes surrounded by an envelope of macrophages known as crown-like structures of the breast (CLS-B). WAT area was measured with NIH Image J. Adipocyte diameter was measured with Canvas 11 Software. Endpoints: 1) CLS-B (+/-) and 2) CLS-B/cm². Clinicopathologic associations with CLS-B were analyzed by logistic regression and Fisher’s exact test. Results: WAT (237 mastectomies, 13 abdominal reconstructions) was obtained from 238 women; median age 48 (range 22 – 90). CLS-B occurrence and number of CLS-B/cm² were greater in overweight/obese (BMI ≥25) and PoM pts compared to lean (BMI <25) and PreM pts (Table). In multivariable analyses, BMI and PoM state were independently associated with CLS-B presence (P<.01 and P=.04) and greater CLS-B/cm²(P<.01 and P=.01). PoM pts had larger mean adipocyte diameter (105.2 +/- 14.0 μ) than PreM pts (95.7 +/- 15.6 μ; P<.01). In pts with bilateral breast WAT and abdominal WAT, concordant CLS status (+/-) was found in 49/63 (78%) and 10/13 (77%) pts, respectively. Conclusions: Breast WAT inflammation (both presence and severity), which we have previously linked to increased aromatase activity, is associated with both increased BMI and menopause. These findings can explain the increased risk of estrogen receptor-positive BC with obesity and PoM status and may also provide targets for rational therapies.