Factors predicting upstaging from clinical N0 to pN2a/N3a in breast cancer patients

Table 2 Comparison between pN1 and pN2a/pN3a

Total (n = 135)	pN1	pN2a/pN3a	P value
	n = 113	n = 22
Age	57.96 ± 12.14	59.64 ± 12.73	0.56
The invasion diameter of the primary lesion (mm)	22.77 ± 14.76	39.86 ± 21.73	< 0.001
Maximal diameter of metastasis in the SLNs	3.46 ± 2.80	9.19 ± 5.66	< 0.001
The number of SLN metastasis			0.014
1	98	14
2 and more	15	8
ER			0.47
Positive	100	18
Negative	11	3
Unknown	2	1
HER2			1
Positive	7	1
Negative	104	21
Unknown	2	0
Nuclear grade of biopsy specimen			0.77
1, 2	87	16
3	21	5
Unknown	4	1
SUVmax of the primary tumor	3.80 ± 2.50	4.13 ± 2.77	0.61
FDG accumulation of axillary lymph nodes			< 0.001
No	104	11
Yes	8	11
Unknown	1	0

ER: Estrogen receptor; HER2: Human epidermal growth factor receptor 2; SLN: Sentinel lymph node; SUV: Standardized uptake value; FDG: Fluorodeoxyglucose.