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

Table 1 Background characteristics of all patients

Background characteristics (n = 135)
Age (yr)	56 (35-84)
SUVmax of primary tumor	3.05 (0.8-11.9)
pN1	113
pN2a or pN3a	22
The invasion diameter of the primary lesion
≤ 20 mm	67
< 50 mm	55
≥ 50 mm	11
NA	2
Maximal diameter of metastasis in the sentinel lymph nodes (mm)	3 (0.1-25)
The number of SLN metastasis
1	112
2	19
3	4
ER
Positive	118
Negative	14
Unknown	3
HER2
Positive	8
Negative	125
Unknown	2
Nuclear grade of biopsy specimen
1, 2	103
3	26
Unknown	6
FDG accumulation of axillary lymph nodes
Yes	19
No	116

SUV: Standardized uptake value; NA: Not applicable; SLN: Sentinel lymph node; ER: Estrogen receptor; HER2: Human epidermal growth factor receptor 2; FDG: Fluorodeoxyglucose.