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Detection of HER‐2/ neu (c‐ erb B‐2) DNA amplification in primary breast carcinoma
Author(s) -
Tsuda Hitoshi,
Akiyama Futoshi,
Terasaki Hiroshi,
Hasegawa Tadashi,
Kurosumi Masafumi,
Shimadzu Mitsunobu,
Yamamori Shunji,
Sakamoto Goi
Publication year - 2001
Publication title -
cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.052
H-Index - 304
eISSN - 1097-0142
pISSN - 0008-543X
DOI - 10.1002/1097-0142(20011215)92:12<2965::aid-cncr10156>3.0.co;2-a
Subject(s) - immunohistochemistry , gene duplication , fluorescence in situ hybridization , kappa , her2/neu , pathology , breast carcinoma , polyclonal antibodies , carcinoma , medicine , breast cancer , microbiology and biotechnology , cancer , antibody , biology , gene , chromosome , immunology , genetics , linguistics , philosophy
BACKGROUND Fluorescent in situ hybridization (FISH) has been shown to be one of the most reliable methods with which to estimate the status of the HER‐2/ neu (or c‐erb B‐2) oncogene at the DNA level. METHODS To study interobserver reproducibility and to determine more clinically correlated criteria for HER‐2/ neu alterations, two observers independently estimated HER‐2/ neu DNA status. The correlation between the consensus HER‐2/ neu DNA status by FISH and HER‐2/ neu protein status detected by immunohistochemistry (IHC) using a polyclonal antibody was studied in 216 surgically resected breast carcinomas and 34 noncancerous tissues. RESULTS According to the HER‐2/CEP17 ratio and mean HER‐2 copies per nucleus, agreement level of HER‐2/ neu amplification was shown to be nearly perfect between two observers (kappa statistic (κ) = 0.94 and κ = 0.84). Finally, 40 tumors (19%) were judged to have HER‐2/ neu DNA amplification, with 6 having low‐level amplification (≥ 2 but < 3 folds) and 34 having high‐level amplification (≥ 3 folds). One hundred seventy‐six other tumors, including 3 tumors that only 1 of the observers determined to be low‐level amplifiers, and 34 noncancerous tissues had no detected amplification. The DNA amplification status was concordant between invasive and intraductal components in 14 carcinomas. HER‐2/ neu protein overexpression of moderate (2+) or high (3+) intensity based on IHC was detected in 51 carcinomas (24%), and was 2+ in 20 carcinomas and 3+ in 31 carcinomas. The HER‐2/CEP17 ratio of ≥ 2 was concordant with IHC findings of 2+/3+ in 91% of carcinomas (195 of 215 carcinomas), with a sensitivity of 70% (35 of 50 carcinomas) and a specificity of 97% (160 of 165 carcinomas). High‐level amplification was detected in 29 of 31 IHC 3+ cases (94%), but in only 5 of 20 IHC 2+ cases (25%) and 0 in 165 IHC 0/1+ cases. All 34 cases with high‐level amplification showed an IHC score of 3+ (29 cases) or an IHC score of 2+ (5 cases), but only 1 case was found to have an IHC score of 3+ and the remainder were IHC 0/1+ in 6 low‐amplification cases. The concordance rate of the high‐level amplification with an IHC score of 3+ was 97% (208 of 215 cases), with a sensitivity of 94% (29 of 31 cases) and a specificity of 97% (179 of 184 cases). CONCLUSIONS The results of the current study indicated that high‐level HER‐2/ neu amplification and an IHC score of 3+ nearly optimally identified breast carcinomas with clinically and biologically significant HER‐2/ neu activation. Conversely, it was confirmed that careful interpretation of test results is required in the case of low‐level amplification and/or an IHC score of 2+. Cancer 2001;92:2965–74. © 2001 American Cancer Society.