Abstract P2-01-29: Axillary involvement in lobular breast cancer
Authors: Zamora Pilar , Marti Covadonga , Roman Ana , Oliver Jose M , de Santiago Javier , Sanchez-Mendez Jose I 
Published: May 2015

Abstract
Purpose:
Since the beginning of the use of the technique of selective sentinel node biopsy (SLNB), multiple models have been proposed to predict both the probability of involvement of the sentinel lymoh node (SLN), and, in case it is positive, the likelihood of non-sentinel lymph node (NSLN) involvement.
Some of the factors that increase the likelihood of SN involvement (multifocallity, hormonal receptors, larger size…)are frequently found in invasive lobular carcinoma.
Invasive lobular carcinoma (ILC) is the second most common histologic type of invasive mammary carcinoma, comprising 5%– 15% of all invasive breast carcinomas. However, in recent decades an increase in the relative incidence of this variant has been reported in the literature. This has been linked to the employment of hormone replacement therapy, the use of assisted reproduction techniques (IVF) or greater availability of diagnostic tools such as breast ultrasound or MRI that allow their better detection.
The aim of this study is to determine the extent of axillary involvement in both SLN and NSLN in patients with ILC
Patients and Methods
369 cases of infiltrating carcinoma candidates for SLNB technique between April 2010 and April 2013 were reviewed retrospectively.
Patients must have a diagnosis of breast cancer of any histological type, with a screening ultrasound without clinical suspicion of axillary involvement.
Cases of intraductal carcinoma that underwent SLNB were excluded and even those that were performed prior to neoadjuvant treatment
Data on age, histological type, positivity / negativity of the SLN, implementation or not of axillary lymphadenectomy and outcome of involvement of NSLN were collected.
Statistical calculations were performed with SPSS.
Results
Of the 369 selected patients, 291 (79.9%) had invasive ductal carcinoma (IDC), 55 (15.1%) ILC and 18 other histological types (mucinous, colloid, tubular, papillary or mixed). The median age was 58.6 years.
SLN could not be found in 5 patientes. 225 (61.8%) had a negative SLN. In 139 (38.2%) patients, SLN was positive, 64 of these cases showed micrometastasis while 75 presented macrometastasis.
Among IDC, 108 (37.1%) of the cases had a positive SLN, 53 (49.1%) of them with macrometastases.
Among ILC, 27 (49.1%) of the cases presented positive SLN, in 20 of them (74.1%) with macrometastasis.
Differences in both the SLN involvement and the presence of macrometastases observed between IDC and ILC were statistically significant (p&lt; 0.001). In those cases were a lymph node dissection was performed, the probability of finding NSLN affection was 18.8% in the case of IDC compared to 55% in patients with ILC (p&lt; 0.001).
Conclusions
Axillary lymph node involvement in the case of candidates for SLNB is more frequent and more extensive in patients with ILC than in patients with IDC.
Citation Format: Pilar Zamora, Covadonga Marti, Ana Roman, Jose M Oliver, Javier de Santiago, Jose I Sanchez-Mendez. Axillary involvement in lobular breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-01-29.