Single-day HER2neu amplification assessment using chip-based digital PCR in formalin-fixed paraffin-embedded breast carcinoma tissue

Figures & data

Figure 1 Study design for HER2 testing by IHC, QuantStudio 3D dPCR, and FISH.

Abbreviations: HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; dPCR, digital PCR; FISH, fluorescence in situ hybridization; FFPE, formalin-fixed paraffin-embedded.

Figure 2 Comparison of processing time for FISH and dPCR.

Abbreviations: FISH, fluorescence in situ hybridization; dPCR, digital PCR; FFPE, formalin-fixed paraffin-embedded.

Table 1 Results of QuantStudio 3D dPCR with respect to IHC data

IHC score	Number of patients	dPCR results
		Mean HER2/RNase P ratio	Minimum HER2/RNase P ratio	Maximum HER2/RNase P ratio
0	26	0.801	0.2311	1.505
1+	9	1.163	0.718	1.721
2+	40	2.256	0.210	14.707
3+	9	6.997	3.032	15.395

Abbreviations: dPCR, digital PCR; IHC, immunohistochemistry; HER2, human epidermal growth factor receptor 2.

Figure 3 Distribution of HER2 dPCR results according to HER2 IHC data.

Note: The two horizontal lines in the graph indicate PCR equivocal range of 1.8–2.0.
Abbreviations: HER2, human epidermal growth factor receptor 2; dPCR, digital PCR; IHC, immunohistochemistry.

Table 2 HER2 distribution by IHC and dPCR

HER2 score (IHC)	dPCR result
	Positive	Negative	Equivocal	Total
Positive (3+)	9	0	0	9
Equivocal (2+)	10	27	3	40
Negative (1+)	0	9	0	9
Negative (0)	0	26	0	26
Total	19	62	3	84

Abbreviations: HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; dPCR, digital PCR.

Figure 4 Correlation of values obtained by FISH HER2/CEP17 ratio and dPCR HER2/RNase P ratio in 76 samples.

Note: The two methods showed high Pearson correlation (r=0.925, p<0.001).
Abbreviations: FISH, fluorescence in situ hybridization; HER2, human epidermal growth factor receptor 2; dPCR, digital PCR.

Figure 5 HER2 expression levels were evaluated by IHC and dPCR in FFPE tissue.

Notes: (A) IHC scoring negative 0 (negative) with dPCR ratio of 0.40 (negative); (B) IHC scoring negative 1+ (negative) with dPCR ratio of 1.00 (negative); (C) IHC scoring 2+ (equivocal) with dPCR ratio of 1.82 (equivocal); and (D) IHC scoring 3+ (positive) with dPCR ratio of 15.39 (positive).
Abbreviations: HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; dPCR, digital PCR.