Table 1.

Incidence of HER2-activating mutations by histology, hormone receptor status, and tumor tissue source for patients whose tumor samples successfully sequenced at GPS laboratory

Positive for HER2 mutation, N (%)P
Histology
 Invasive ductal carcinoma (n = 309)5 (1.6%)0.026a
 Invasive lobular carcinoma (n = 51)4 (7.8%)
 Invasive ductal/lobular carcinoma (n = 12)0 (0%)
 Otherb (n = 9)0 (0%)
Hormone receptor status
 ER+ and/or PR+ (n = 277)9 (3.2%)0.219
 ER PR HER2 (n = 82)0 (0%)
 Unknown (n = 17)0 (0%)
Samples tested
 Primary breast cancer (n = 256)6 (2.3%)>0.99
 Metastatic site (n = 125)3 (2.4%)
Total (n = 381)9
  • aComparison between ductal carcinoma (n = 309) vs. lobular carcinoma (n = 51).

  • bOthers include metaplastic (n = 2); mucinous (n = 3); and unknown (n = 4).