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Table 2 Classifications of mammographic density

From: Mammographic density, breast cancer risk and risk prediction

  Qualitative Quantitative
  Wolfe BI-RADS Planimeter Computer-assisted thresholding method Visual estimation
Description Visual classification of the mammographic image into four categories based on extent and distribution of the parenchyma, including ducts, nodular, homogeneous densities, and fat. Standardized reporting of visual assessment of mammographic findings by the American College of Radiology BI-RADS. Both breasts are used for the BI-RADS An acetate overlay is placed over the mammogram image to outline the breast, and an expert reader traces the areas of breast density. The total breast and dense areas are measured with an outlining tool. Mammographic films are digitized, and two threshold values are selected. The first separates the breast from background, and the second identifies the edges of the regions representing radiographically dense tissue. The numbers of pixels comprising the total breast area and those for dense area are calculated. Results can be reported as percentage density (the ratio of the dense pixels to total breast area) or absolute area of density (in pixels, square centimeters or square millimeters) Radiologist or expert reader subjectively assigns a percentage density corresponding to the proportion of breast that is dense.
Categorization N1 – Completely fatty breast
P1 – Mainly fatty breast with prominent ducts, up to 25% density
P2 – Prominent ducts, more than 25% density
DY – No visible ducts, diffuse and extensive nodular density [64].
Category 1 – Almost entirely fatty (<25% dense)
Category 2 – Scattered fibroglandular densities (approximately 25%–50% dense)
Category 3 – Heterogeneously dense (approximately 51%–75% dense)
Category 4 – Extremely dense (>75% dense) [65].
Percentage density on a continuous scale (0%–100%).
Can be categorized for analyses (such as 0%, 1%–24%, 25%–49%, 50%–74%, 75%) [4].
Percentage density (0%–100%) or absolute area of density (in pixels, square centimeters or square millimeters) on continuous scale [60]. Both measures can also be categorized.
Percentage or absolute density can be categorized.
Visually estimated directly into categories (such as 0%, <10%, 10%–<25%, 25%–<50%, 50%–<75%, >75%) [6].
  1. BI-RADS, Breast Imaging Reporting and Data System.