Development of an easy method to test for HER2 in breast cancer using dual-color in situ hybridization.
BACKGROUND
Although human epidermal growth factor receptor 2 (HER2) is a significant clinical biomarker for breast cancer, the HER2 testing involves a complicated evaluation process. We devised an easy method for HER2 gene testing and investigated its utility.


METHODS
HER2 testing was performed by immunohistochemistry (IHC) and dual-color in situ hybridization (DISH) on surgical specimens from 50 patients with invasive breast cancer. DISH was evaluated by two methods. One was the DISH count method in which the HER2 and CEP17 signals were counted and the HER2/CEP17 signal ratio was calculated. The other was the DISH-easy method in which pathologists only observed slices without counting the signals. The DISH-easy method was performed by two pathologists. We analyzed the correlations between the DISH-easy method and the DISH count method by each pathologist and calculated the inter-observer concordance rate of the DISH-easy method.


RESULTS
The results from two pathologists using the DISH-easy method corresponded to the IHC results (P < 0.01) and the DISH count method results (P < 0.01). All cases determined to be negative using the DISH-easy method were also negative via the DISH count method with a corresponding rate of 100 % for both pathologist A (34/34) and B (32/32). Most of the results for the positive cases also corresponded; the correspondence rate of pathologist A was 100 % (8/8) and 89 % for B (8/9). The inter-observer concordance rate was 81 % (κ = 0.65).


CONCLUSIONS
The DISH-easy method is simple and useful for HER2 testing regardless of proficiency of the evaluators.
Department of Pathology, Cancer Institute, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo, 135-8550, Japan.|Department of Breast Oncology, Juntendo University School of Medicine, Tokyo, Japan.
Tomoe
T
Nakagawa
Department of Pathology, Cancer Institute, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo, 135-8550, Japan. rhorii-pathology@jfcr.or.jp.|Department of Pathology, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan. rhorii-pathology@jfcr.or.jp.
Rie
R
Horii
Breast Oncology Center, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan.
Yoshinori
Y
Ito
Breast Oncology Center, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan.
Takuji
T
Iwase
Department of Pathology, Cancer Institute, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo, 135-8550, Japan.|Department of Pathology, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan.
Futoshi
F
Akiyama
D002288:Adenocarcinoma, Mucinous / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002291:Carcinoma, Papillary / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D008875:Middle Aged; D060787:Neoplasm Grading; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism
D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human
Breast cancer; Dual-color in situ hybridization; HER2 testing; Human epidermal growth factor receptor 2