Association between mammographic density and age-related lobular involution of the breast.
OBJECTIVE
Mammographic density and lobular involution are both significant risk factors for breast cancer, but whether these reflect the same biology is unknown. We examined the involution and density association in a large benign breast disease (BBD) cohort.


METHODS
Women in the Mayo Clinic BBD cohort who had a mammogram within 6 months of BBD diagnosis were eligible. The proportion of normal lobules that were involuted was categorized by an expert pathologist as no (0%), partial (1% to 74%), or complete involution (>or= 75%). Mammographic density was estimated as the four-category parenchymal pattern. Statistical analyses adjusted for potential confounders and evaluated modification by parity and age. We corroborated findings in a sample of women with BBD from the Mayo Mammography Health Study (MMHS) with quantitative percent density (PD) and absolute dense and nondense area estimates.


RESULTS
Women in the Mayo BBD cohort (n = 2,667) with no (odds ratio, 1.7; 95% CI, 1.2 to 2.3) or partial (odds ratio, 1.3; 95% CI, 1.0 to 1.6) involution had greater odds of high density (DY pattern) than those with complete involution (P trend < .01). There was no evidence for effect modification by age or parity. Among 317 women with BBD in the MMHS study, there was an inverse association between involution and PD (mean PD, 22.4%, 21.6%, 17.2%, for no, partial, and complete, respectively; P trend = .04) and a strong positive association of involution with nondense area (P trend < .01). No association was seen between involution and dense area (P trend = .56).


CONCLUSIONS
We present evidence of an inverse association between involution and mammographic density.
Ghosh
Karthik
K
Division of General Internal Medicine, Department of Internal Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA.
Hartmann
Lynn C
LC
Reynolds
Carol
C
Visscher
Daniel W
DW
Brandt
Kathleen R
KR
Vierkant
Robert A
RA
Scott
Christopher G
CG
Radisky
Derek C
DC
Sellers
Thomas A
TA
Pankratz
V Shane
VS
Vachon
Celine M
CM
D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D001706:Biopsy; D001941:Breast Diseases / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D016009:Chi-Square Distribution; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008327:Mammography; D008875:Middle Aged; D016017:Odds Ratio; D010298:Parity; D011237:Predictive Value of Tests; D011247:Pregnancy; D018570:Risk Assessment; D012307:Risk Factors