Table 3.

Results from comparing HER2 levels in primary tumors and macrometastases with regard to HER2-low.

Metastases in the ipsilateral lymph node Number of cases, n (%)
	HER2 protein levels	0	1+	2+	3+	Total
Primary tumor
	0	8 (72.7)	6 (54.5)	2 (18.2)	0 (0.0)	11a
	1+	9 (56.3)	11 (68.8)	7 (43.8)	0 (0.0)	16b
	2+	0 (0.0)	4 (57.1)	6 (85.7)	0 (0.0)	7c
	3+	1 (11.1)	0 (0.0)	2 (22.2)	6 (66.7)	9
	43
	Number of metastases, n (%)
	HER2d	Negative	Low		Positive	Total
	Negative	55 (84.6)	10 (15.4)		0 (0.0)
						65
	Low	16 (15.8)	85 (84.2)		0 (0.0)
						101
	Positive	4 (10.0)	6 (15.0)		30 (75.0)
						40
	206
	HER2 protein levels	0	1+	2+	3+
	0	55 (84.6)	8 (12.3)	2 (3.1)	0 (0.0)
						65
	1+	16 (22.9)	26 (37.1)	28 (40.0)	0 (0.0)
						70
	2+	0 (0.0)	10 (32.3)	21 (67.7)	0 (0.0)
						31
	3+	4 (10.0)	0 (0.0)	6 (15.0)	30 (75.0)
						40
	206

a) Two cases with HER2 0 primary tumors had both macrometastases that were HER2 1+ and macrometastases that were 2+. Three cases with HER2 0 primary tumors had both macrometastases that were HER2 1+ and macrometastases that were 0.

b) Four cases with HER2 1+ primary tumors had both macrometastases that were HER2 1+ and macrometastases that were 0. Three cases with HER2 1+ primary tumors had both macrometastases that were HER2 1+ and macrometastases that were 2+. Two cases with HER2 1+ primary tumors had macrometastases that were HER2 1+, macrometastases that were 0, and macrometastases that were 2+.

c) Three cases with HER2 2+ primary tumors had both macrometastases that were HER2 1+ and macrometastases that were 2+.

d) Negative: HER2 0. Low: HER2 1+ or 2+ and not amplified, i.e., HER2/CEP7 ratio <2 or HER2/CEP17 ratio ≥2 and an average HER2 copy number <4.0. Positive: HER2 3+.