Abstract P3-01-15: Molecular subtypes and axillary metastases in breast cancer
Authors: Sánchez-Méndez JI , Alonso P , Martí C , Pinto A , Escabias C , Espinosa E , De Santiago J , Zamora P 
Published: May 2016

Abstract
Objective
To assess differences in axillary infiltration (global, sentinel, and non-sentinel lymph nodes) according to breast cancer molecular subtype.
Material and methods
Patients with infiltrating breast carcinoma diagnosed in the years 2011 to 2014 in our institution were included. Sentinel lymph node biopsy (SLNB) was performed in all patients staged N0 by clinical examination and axillary ultrasound. One-step nucleic acid amplification (OSNA) was performed in cases positive for cytokeratin-19. Complete lymphadenectomy was done in patients with axillary macrometástasis and, until February 2012, also in those with micrometastasis in the SLNB. Immunohistochemistry-based St. Gallen 2013 criteria were used to assign the molecular subtype (hormonal receptors, ki67 and HER2).
Results
Overall 720 patients were included, 53.9% of whom had axillary infiltration (75.8% macrometastases). Axillary infiltration was most common in the HER2 subtype -82.1% (91.3% macrometastases) and least common in the basal subtype -42.7%.
Global and Sentinel nodeFENOTYPELUMINAL ALUMINAL BLUM B HER2HER 2BASALTOTAL Axilla312255502875720 Negative160 (51.3%)103 (40.4%)21 (42.0%)5 (17.9%)43 (57.7%)33246.1%Positive152 (48.7%)152 (59.6%)29 (58.0%)23 (82.1%)32 (42.3%)38853.9% Macrom.112 (73.7%)115 (75.7%)23 (79.6%)21 (91.3%)23 (71.9%)29475.8%Microm40 26.3%)37 24.3%)6 (20.3%)2 (8.7%)9 (28.1%)9424.2% Sentinel Node23415817734450 Negative152 (65%100 (63.3%)12 (70.6)6 (85.7%)22 (64.7%)29264.9%Positive82 (35%)58 (36.7%)5 (29.4)1 (14.3%)12 (35.3%)15835.1% Macrom44 (53.7%)26 (44.8%)2 (40%)0 (0.0%)4 (33.3%)7648.1%Microm38 (43.3%)32 (55.2%)3 (60%)1 (100%)8 (66.7%)8251.9%
On the contrary, the HER2 subtype had the lowest risk of axillary infiltration in patients subjected to SLNB (14.3%). No differences were seen in the other subtypes subjected to SLNB.
90 patients underwent complete lymphadenectomy. Positive non-sentinel lymph nodes were most commonly seen in luminal A tumors (30%).
Non Sentinel NodesFENOTYPELUMINAL ALUMINAL BLUM B HER2HER 2BASALTOTAL Non SN503320590 Negative35 (70%)27 (81.8%)2 (100%)04 (80%)6875.6%Positive15 (30%)6 (18.2%)001 (20%)2224.4% Macrom.14 (93.3%)5 (83%)001 (100%)2090.9%Microm1 (6.7%)1 (16,7%)00029.1%
Conclusions
1. Significant differences in axillary infiltration were seen according to molecular subtypes.
2. Most HER2+ tumors had N+ disease detected by ultrasound. However, in those HER2+ with negative ultrasound, the SLNB was usually negative. If positive, non-sentinel lymph nodes were most commonly negative.
3. Half of luminal A tumors had N+ disease detected by ultrasound. In the other half, there was an increased risk of positive SLNB and non-sentinel lymph nodes with regard to other subtypes.
Citation Format: Sánchez-Méndez JI, Alonso P, Martí C, Pinto A, Escabias C, Espinosa E, De Santiago J, Zamora P. Molecular subtypes and axillary metastases in breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-01-15.