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Table 3 Distribution of breast cancer cases from six studies by age and tumor characteristics

From: Mammographic density and risk of breast cancer by age and tumor characteristics

Tumor type Age <55 years Age 55 to 64 years Age ≥65 years
N % N % N %
Total controls 3,373 68.8 2,031 66.5 1,795 67.6
Total cases 1,533 31.2 1,021 33.5 860 32.4
   Invasive 1,227 80.0 858 84.0 760 88.4
   In situ 295 19.2 160 15.7 100 11.6
   Unknown 11 0.7 3 0.3 0 0.0
Tumor characteristics
Histology
   Ductal 988 80.5 654 76.2 545 71.7
   Lobular 123 10.0 110 12.8 114 15.0
   Mixed 65 5.3 55 6.4 51 6.7
   Unknown/Other 51 4.2 39 4.6 50 6.6
Histologic grade
   Well differentiated 292 23.8 248 28.9 259 34.1
   Moderately differentiated 466 38.0 320 37.3 295 38.8
   Poorly differentiated 342 27.9 165 19.2 134 17.6
   Unknown 127 10.4 125 14.6 72 9.5
Tumor size
   0.1 to 1.0 cm 378 30.8 312 36.7 279 36.7
   1.1 to 2.0 cm 496 40.4 330 39.3 299 39.3
   2.1+ cm 310 25.3 184 20.7 157 20.7
   Unknown 43 3.5 32 3.3 25 3.3
Involvement of lymph nodes
   Negative 810 66.0 610 71.1 500 65.8
   Positive 347 28.3 192 22.4 148 19.5
   Unknown 70 5.7 56 6.5 112 14.7
Estrogen receptor status
   Negative 228 18.6 139 16.2 82 10.8
   Positive 949 77.3 674 78.6 644 84.7
   Borderline/Unknown 50 4.1 45 5.2 34 4.5
Progesterone receptor status
   Negative 329 26.8 232 27.0 157 20.7
   Positive 844 68.8 580 67.6 566 74.5
   Borderline/Unknown 54 4.4 46 5.4 37 4.9
HER2 status
   Negative 674 54.9 359 41.8 383 50.4
   Positive 142 11.6 63 7.3 65 8.6
   Borderline/Unknown 411 33.5 436 50.8 312 41.1
  1. HER2, human epidermal growth factor receptor 2.