Comparison of fluorescence in situ hybridization and immunohistochemistry for assessment of HER-2 status in breast cancer patients

Discordance Between Immunohistochemistry and In Situ Hybridization to Detect HER2 Overexpression/Gene Amplification in Breast Cancer in the Modern Age: A Single Institution Experience and Pooled Literature Review Study

BACKGROUND

Human epidermal growth factor 2 (HER2) amplification and/or overexpression occurs in 12% to 25% of breast cancers. Accurate detection of HER2 is critical in predicting response to HER2-targeted therapy. Both immunohistochemistry (IHC) and in situ hybridization (ISH) are FDA-approved methods for detecting HER2 status because its protein overexpression is largely attributable to gene amplification. However, variable discordant results between IHC and ISH have been reported.

METHODS

We determined the frequency of HER2 IHC/ISH discordance in these patients and also performed a pooled literature review analysis.

RESULTS

Of the 1125 consecutive primary or metastatic breast cancers with HER2 IHC and ISH performed simultaneously between 2015 and 2020, 84.6% had an unequivocal HER2 status. Discordance was found in 30 cases from 26 patients, including 13 IHC^-/ISH⁺ and 17 IHC⁺/ISH^-, representing 1.6% and 11.9% of IHC^- and IHC⁺ cases, respectively. Review of the literature between 2001 and 2020 identified 46 relevant studies, with a total of 43,468 cases with IHC and ISH performed. The IHC^-/ISH+ and IHC⁺/ISH^- discordances were seen in all antibody clones and ISH methods used. The IHC⁺/ISH^- discordance was significantly higher than IHC^-/ISH⁺ (13.8% vs. 3%, P < .0001). The overall discordance constituted 4% of all cases and 5.4% of those with an unequivocal IHC status. Significantly lower incongruities for both IHC^-/ISH⁺ and IHC⁺/ISH^- were found in those published after 2018. The discordances probably reflect altered biology of HER2 oncogene/oncoprotein. Routinely performing both IHC and ISH may uncover such cases to prevent denial of potentially beneficial targeted therapy.

Assessment of Her-2/neu status using immunocytochemistry and fluorescence in situ hybridization on fine-needle aspiration cytology smears: experience from a tertiary care centre in India

Breast carcinoma shows amplification/overexpression of Her-2/neu in ∼20-30% of cases. The determination of Her-2/neu expression accurately is vital in clinical practice as it has significant predictive value and eligibility for anti Her-2/neu therapy. Amplification and overexpression of Her-2/neu gene is traditionally identified by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) on tissue sections; only a few studies have evaluated feasibility of these techniques on cytological smears. One hundred cases of breast cancer with fine-needle aspiration cytology (FNAC) samples and corresponding surgically resected specimen were selected. Immunocytochemistry (ICC) and FISH for Her-2/neu was done on FNA smears, whereas IHC was performed on corresponding tissue sections. Diagnostic accuracy of ICC was 99% when compared with IHC. Comparison of FISH results with IHC showed 100% concordance. Unlike many centers in West, FNAC is still routinely performed in developing countries like India where vast majority of breast cancer cases present as palpable lumps. The high rates of accuracy of ICC and FISH for Her-2/neu detection can make FNAC a relevant first line of investigation as a cost effective model with a rapid turn-around time, providing complete information necessary for initial management of breast cancer patients.

Assessment of Her-2/neu gene amplification status in breast carcinoma with equivocal 2+ Her-2/neu immunostaining

BACKGROUND AND PURPOSE

Amplification of Her-2/neu gene occurs in 25-30% of breast carcinomas. FDA approved trastuzumab (Herceptin) is effective only in tumors having the gene amplification. Immunohistochemistry (IHC) for Her-2/neu protein is widely used but false positive and false negative results exist. Fluorescence in-situ hybridization (FISH) has both excellent sensitivity and specificity in detecting Her-2/neu amplification. Comparative studies have shown discordant results in proportion of cases with equivocal 2+ immunostain. This study is thus conducted to ascertain the frequency of Her-2/neu gene amplification by FISH in breast carcinoma specified as score 2+ by IHC and to correlate these findings with parameters of prognosis in breast cancer.

METHODS

From October 2008 till May 2010 all paraffin blocks from cases with invasive breast carcinoma which were scored as 2+ by IHC were eligible for the study, there were 50 cases. Immunohistochemical evaluation of Her-2/neu was performed using the HercepTest. All cases were immunohistochemically evaluated for ER and PR. FISH was performed using FDA approved Path-Vysion Her-2/neu/CEP 17 dual color probe.

RESULTS

Nine cases (18%) out of 50 cases scored as Her-2/neu 2+ by IHC showed true gene amplification with a median value of scoring ratio 4.28 ranging from 2.37 to 13.26. Another two cases showed low level of amplification but when corrected for Her-2/neu/CEP ratio they did not show true amplification as they were associated with polysomy 17. With the exception of tumor size, neither patient's age, histologic grade nor lymph node status were correlated with Her-2/neu gene amplification. Significant inverse correlation existed between Her-2/neu gene amplification and ER (P=0.01), PR status (P<0.001).

CONCLUSION

Even though FISH is a more complex and expensive procedure, it should be considered the method of choice for assessment of Her-2/neu gene status especially for equivocal cases by IHC that are not accompanied by true gene amplification in the majority of breast carcinoma cases.

HER2 status in operable breast cancers from Vietnamese women: Analysis by immunohistochemistry (IHC) and automated silver enhanced in situ hybridization (SISH)

BACKGROUND

HER2 amplification has been reported to occur in 19-30% of breast cancers in women from Western countries. Little is known about the HER2 status in breast cancers from Vietnamese women. The aim of this study was to assess the HER2 status in Vietnamese women with operable breast cancer using immunohistochemistry and silver in situ hybridization techniques.

MATERIAL AND METHOD

Tissue blocks from 242 Vietnamese women with invasive primary breast carcinoma were stained by immunohistochemistry (IHC) and a dual silver in situ hybridization (SISH) for assessing HER2 status. The analysis followed international recommendations with a semi-quantitative grading of the reaction in four levels, "0", "1+", "2+" and "3+". The HER2 gene amplification was assessed by calculating the ratio of HER2/chromosome 17 in 20 tumor cell nuclei. A ratio of <1.8 was classified as non-amplification and a ratio >2.2 indicated tumors with gene amplification. A ratio between 1.8 and 2.2 was equivocal.

RESULTS

Using IHC, 39% of the tumors strongly expressed "3+" the HER2 protein. An intermediate level "2+" of the protein was found in 11% while 50% showed no or low "0/1+" levels of protein expression. Gene amplification was found in 95% and 46% of the tumors with high "3+" and intermediate "2+" levels of protein expression, respectively. Thus, 41% of the patients had tumors with HER2 amplification. The concordance between IHC and SISH was 87%. Gene amplification was more frequent in ER negative than in ER positive tumors, 57% versus 33%, respectively. Additionally, tumors from postmenopausal women were amplified in 55% as compared to 36% in premenopausal women.

CONCLUSIONS

HER2 gene amplification was found in 41% of Vietnamese breast cancers; this level is considerably higher than that previously found in a series of Swedish breast cancer women. The HER2-positive tumors were more often found in post-menopausal women than in ER negative tumors.

Reproductive Factors, Steroid Receptor Status, and Tumour Markers of HER2-Positive Breast Cancer in Northern China

Background

Although China has a breast cancer incidence that surpasses all other cancer registries, there have been few reports to evaluate the relationships of reproductive history, steroid receptor status, and tumour markers with HER2 status of breast cancer.

Patients and Methods

This project included 274 primary invasive ductal breast cancer patients. Information concerning the reproductive factors and tumour characteristics of the patients had previously been collected. HER2 and steroid receptor status were detected in tumour tissues. Serum CEA, CA15-3, and CA125 levels were analyzed for all patients.

Results

Younger age at menarche was observed in patients with HER2-positive than in those with HER2negative status (p = 0.03). Statistically significant differences were found between the HER2-positive group and HER2-negative group for estrogen receptor (ER) and progesterone receptor (PR) status (p < 0.01). Age of onset, other reproductive factors, tumour characteristics, and serum tumour marker level were not significantly different between those patients with HER2-positive and those with HER2-negative status.

Conclusion

We confirm that age at menarche may plausibly be differentially correlated with the risk of HER2-positive invasive ductal breast cancer because it is presumed to impact exposure to endogenous sex hormones. HER2 is inversely related to ER and PR in invasive ductal breast cancer patients of Northern China.