Boyd N F, Lockwood G A, Byng J W, Tritchler D L, Yaffe M J
Division of Epidemiology and Statistics, Ontario Cancer Institute, Toronto, Canada.
Cancer Epidemiol Biomarkers Prev. 1998 Dec;7(12):1133-44.
The radiological appearance of the female breast varies among individuals because of differences in the relative amounts and X-ray attenuation characteristics of fat and epithelial and stromal tissues. Fat is radiolucent and appears dark on a mammogram, and epithelium and stroma are radiodense and appear light. We review here the evidence that these variations, known as mammographic parenchymal patterns, are related to risk of breast cancer. Studies that used quantitative measurement to classify mammographic patterns have consistently found that women with dense tissue in more than 60-75% of the breast are at four to six times greater risk of breast cancer than those with no densities. These risk estimates are independent of the effects of other risk factors and have been shown to persist over at least 10 years of follow up. Estimates of attributable risk suggest that this risk factor may account for as many as 30% of breast cancer cases. Mammographically dense breast tissue is associated both with epithelial proliferation and with stromal fibrosis. The relationship between these histological features and risk of breast cancer may by explained by the known actions of growth factors that are thought to play important roles in breast development and carcinogenesis. Mammographically dense tissue differs from most other breast cancer risk factors in the strength of the associated relative and attributable risks for breast cancer, and because it can be changed by hormonal and dietary interventions. This risk factor may be most useful as a means of investigating the etiology of breast cancer and of testing hypotheses about potential preventive strategies.
由于脂肪、上皮组织和基质组织的相对含量以及X线衰减特性存在差异，女性乳房的放射学表现因人而异。脂肪在X线下呈透光性，在乳房X线照片上显示为暗色，而上皮组织和基质在X线下呈致密性，显示为亮色。我们在此回顾一下这些被称为乳房X线实质模式的变化与乳腺癌风险相关的证据。采用定量测量对乳房X线模式进行分类的研究一致发现，乳房60%-75%以上为致密组织的女性患乳腺癌的风险是无致密组织女性的四至六倍。这些风险评估独立于其他风险因素的影响，并且已证实在至少10年的随访期内持续存在。归因风险估计表明，这一风险因素可能占乳腺癌病例的30%。乳房X线致密的乳腺组织与上皮细胞增殖和基质纤维化均有关联。这些组织学特征与乳腺癌风险之间的关系或许可以通过生长因子的已知作用来解释，这些生长因子被认为在乳腺发育和致癌过程中发挥重要作用。乳房X线致密组织与大多数其他乳腺癌风险因素不同，其与乳腺癌相关的相对风险和归因风险强度较高，而且它可以通过激素和饮食干预加以改变。这一风险因素作为研究乳腺癌病因以及检验潜在预防策略假说的手段可能最为有用。
