An area of focal fibroglandular tissue lacking the discrete borders of a mass is referred to as an asymmetry if seen on 1 projection or focal asymmetry if seen on 2 projections. At this point, there is no reason to get overly concerned. Just make sure you return to get the recommended diagnostic mammogram. Most of the time those focal asymmetries press out with spot compression views, suggesting normal superimposed fibroglandular tissue. If the abnormality persists with spot compression, then the next step would be biopsy.
Every mammography report includes 1 of 4 breast composition categories:
a. The breasts are almost entirely fatty.
b. There are scattered areas of fibroglandular density.
c. The breasts are heterogeneously dense, which may obscure small masses.
d. The breasts are extremely dense, which lowers the sensitivity of mammography.
The first 2 are considered not dense; the latter 2 are considered dense.
The more dense a breast is, the harder it is to detect underlying masses.
This breast composition category has nothing to do with why you were called back.
It is used more as a qualifier to explain the study's limitations.