1 2 3 4 5 6 10 11 14 15 Patients And Methods Patients n 16 SN Biopsy Technique 16 99m Histopathological Evaluation 16 18 th Clinicopathological Features 19 neu SN and Non-SN Characteristics th 20 21 1 11 2 tumor penetrative depth 12 FIG. 1. Pattern of distribution of metastatic breast cancer deposits in SNs.  FIG. 2. arrow  Non-SN characteristics included the total number of non-SNs, maximal tumor diameter, AJCC classification, and ECE. If more than one non-SN was involved, the largest diameter was recorded. Statistical Analysis neu U P Results 1 1 2 TABLE 1. Clinicopathological characteristics of 357 invasive breast cancer patients with a positive SN and subsequent axillary lymph node dissection Feature No. % Mean age (range) 54 y (22–86)  Primary tumor Mean tumor size (range) 2.4 cm (0.3–9.0)   pT1 187 52   pT2 150 42   pT3 19 5   pTx 1 0 Histological subtype   Invasive ductal cancer 298 84    Invasive lobular cancer 36 10   Others 23 6 Histological grade (B&R)   1 74 21   2 161 45   3 122 34 2 13 (0–102) Steroid receptor status   ER – positive ‡ 322 90   ER – negative 34 10   ER – unknown  1    PR – positive ‡ 284 80   PR – negative 70 20   PR – unknown 3  neu   Positive 26 15   Negative 150 85   Unknown 181  ‡ ≥10% immunoreactive neoplastic cells. TABLE 2. SN and non-SN characteristics of 357 invasive breast cancer patients with a positive SN and subsequent axillary lymph node dissection Feature  No.  % SN Total number of SNs 571 Mean number of SNs  1.6 Total number of positive SNs 419 Mean diameter SN metastases  4.7 mm AJCC classification of SN metastatic size    ITC 24 7   Micrometastasis 112 31   Macrometastasis 221 62 Extracapsular extension    No 257 72   Yes 100 28 Microanatomic location   Subcapsular 167 47   Parenchymal  11 3   Combined 40 11   Extensive 139 39 Mean penetrative depth 2.9 mm  Non-SNs Total number of non-SNs 4939  Mean number of non-SNs (range) 14 (5–38)  Total number of positive non-SNs 474  Total number of negative non-SNs 4465  Size of non-SN metastases   ITC 3 2   Micrometastases 33 24   Macrometastases 100 74 3 4 neu TABLE 3. Comparison of categorical clinicopathological and SN characteristics in invasive breast cancer patients without and with non-SN metastases by Pearson chi-square test  Without non-SN metastases With non-SN metastases P  Feature No (%) No (%)  Total  221 (62) 136 (38)  Histological subtype   0.914   Ductal 183 (51) 115 (32)    Lobular 22 (6) 14 (4)    Others 16 (5) 7 (2)  Histological grade (B&R)   0.798 ER positive 198 (56)  124 (35) 0.715   Negative 22 (6) 12 (3)  PR positive 179 (50) 106 (30) 0.589   Negative 41 (12) 29 (8)  neu 16 (9) 10 (6) 0.670   Negative 83 (47) 67 (38)  No. of SN   0.246   1 131 (37) 89 (25)    >1 90 (25) 47 (13)  No. of involved SN    0.050   1 198 (55) 112 (31)    >1 23 (6) 24 (7)  AJCC SN metastases   <0.001   ITC 21 (6) 3 (1)    Micrometastasis 86 (24) 26 (7)    Macrometastasis 114 (32) 107 (30)  Extracapsular extension   <0.001   No 175 (49) 82 (23)    Yes 46 (13) 54 (15)  Microanatomic location SN metastases   <0.001   Subcapsular 126 (35) 41 (11)    Combined 23 (6) 17 (5)    Parenchymal 8 (2) 3 (1)    Extensive 64 (18) 75 (21)  Multifocality   0.087    No 176 (49) 118 (33)    Yes 45 (13) 18 (5)  TABLE 4. Comparison of continuous clinicopathological and SN characteristics in invasive breast cancer patients without and with non-SN metastases by Mann–Whitney U-test  Without non-SN metastases With non-SN metastases P  Feature Total no. (%) 221 (62) 136 (38)  Age (years, mean) 54 53 0.249 Primary tumor diameter, cm (mean) 2.3 2.5 0.019 2 13 12 0.693 SN tumor diameter, mm (mean)  3.6 6.5 <0.001 SN tumor penetrative depth, mm (mean)  2.2 3.9 <0.001 P N N N P 3 FIG. 3. Flow chart showing distribution of SN AJCC classification according to non-SN involvement.  N N N N 3 N N  N P 5 4 TABLE 5. Predictive value of penetrative depth of SN metastases for non-SN involvement in patients with invasive breast cancer SN penetrative depth (mm) N No. of patients with non-SN involvement (%) <0.155 29 3 (10) 0.155–2.7 181 51 (28) >2.7 147 82 (56) FIG. 4. P  P P 6 N N N .  N N N N TABLE 6. Predictive value of a combination of AJCC classification of SN metastases and penetrative depth of SN metastases for non-SN involvement in patients with invasive breast cancer  N No. of patients with non-SN involvement (%) ITC/SN penetrative depth < 2.7 mm or Micrometastases/penetrative depth < 0.155 mm 38 4 (11) Micro- or macrometastases/penetrative depth 0.155–2.7 mm 172 50 (29) Micro- or macrometastases/penetrative depth >2.7 mm 147 82 (56) Discussion 22 ,  23 24 11 13 The measurement of the SN tumor penetrative depth was difficult in many cases, especially in case of extensive tumor deposits. In these cases the tumor deposits frequently extended beyond the center of the lymph node, making it difficult to determine which edge of the SN capsule should be used to measure the tumor penetrative depth. Similar difficulties were encountered when the SN had a lobulated outline. Further studies which more rigorously define the tumor penetrative depth may strengthen its predictive power and reproducibility. In conclusion, patients with breast carcinoma and SN involvement can be stratified into subgroups at significantly different risk for non-SN involvement, according to microanatomic localization of the SN metastatic deposits and penetrative depth into the SN. However, based on these features no subgroup of patients could be selected without non-SN involvement.