Multiple examples show the range of percent breast volume occupied
by dense tissue in cases from fatty replaced (10%) to densely opacified breast
tissue (90%).
Images:
1: 10% R,L CC 
2: 20% R,L CC
3: 30% R,L CC
4: Male 30% R,L LM
5: 30% R, 40% L CC
6: 40% R,L CC
7: 50% R,L CC
8: 60% R,L LM
9: 70% R,L OBL
10: 70% R, 80% L OBL
11: 80% R,L CC
12: 90% R,L OBL
DIAGNOSIS:
Bilateral views from multiple different cases show the range of percentage of
breast volume occupied by dense tissue in normal and a few abnormal cases.
FINDINGS:
1. 10% of breast volume occupied by dense tissue on right and left CC views.
2. 20% of breast volume occupied by dense tissue on right and left CC views.
3. 30% of breast volume occupied by dense tissue on right and left CC views.
4. 30% of breast volume occupied by dense tissue on right and left LM views. This male patient had recent enlargement of the left breast with firm tissue palpable in the retroareolar region. This was found to be benign gynecomastia on the left. A mammogram of the contralateral breast was done only for comparison to the palpable left breast lesion (checking for asymmetry). The right breast unexpectedly contained occult intraductal carcinoma with extensive microcalcifications. The patient had only a biopsy for the gynecomastia on the left but had a mastectomy for the incidentally detected breast carcinoma on the right.
5. Mild asymmetry on CC views with 30% of the right and 40% of the left breast volume occupied by dense tissue. Note the abnormally prominent interstitial pattern on the left. The findings on the left are typical radiation therapy changes after treatment for breast cancer.
6. 40% of breast volume occupied by dense tissue on right and left CC views.
7. 50% of breast volume occupied by dense tissue on right and left CC views.
8. 60% of breast volume occupied by dense tissue on right and left lateromedial views.
9. 70% of breast volume occupied by dense tissue on right and left OBL views.
10. 70% of the right and 80% of the left breast volume is occupied by dense tissue. The slight asymmetry on these oblique views was due to an large, complicated cyst located in the central left breast and retroareolar region.
11. 80% of breast volume occupied by dense tissue on normal right and left CC views. Only a few small areas of fat lucency remain.
12. 90% of breast volume occupied by dense tissue on normal right and left OBL views (almost no fat lucency remains visible).
DISCUSSION:
Routinely estimating the percent (10% to 90%) of breast volume occupied by
dense tissue can be useful in several mammographic situations. The most common
is hormone replacement therapy (HRT) induced mammographic changes. HRT can cause
an increase in 10% to as much as 50% in breast density from before to after
starting treatment. Most of this change usually occurs in the first 6 months to
4 years. Attempting to quantitatively estimate this percent will usually lead
to the awareness that new nodularity or neodensity is not unilateral
(worrisome) but is bilateral and diffuse. If the patient history data sheet
shows a clinical history of starting HRT in the past 4 years, bilateral
increase in density is less worrisome.
For radiation therapy patients, the percent density of the treated breast can increase 10% to 40% during the initial months of therapy. Reporting the percent change may be clinically useful because the density will normally begin to gradually decrease over the next 1 to 3 years. It may or may not eventually return to pretreatment density depending on dose and other factors. If this sequence varies, a recurrence of the carcinoma or other complication may be developing.
The percent density is only reproducible plus or minus 10% so it is not
useful to report it with smaller percentages. Variation of 10% can be due to
routine minor variations in radiographic technique and equipment. Year to year
comparisons of one patient
Submitted by:
Ralph L. Smathers, M.D.
Mammography Specialists Medical Group Inc.