Impact of Molecular Subtypes of Breast Cancer on Axillary Lymph Node Metastasis: A Tertiary Center Experience

Background: Axillary lymph node metastasis (ALNM) is one of the important prognostic factors of breast cancer. The objective of this study was to assess the risk of ALNM in different molecular subtypes determined by estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (her2neu) of breast cancer.Methods: This retrospective study was conducted on patients who had undergone upfront breast conserving surgery (BCS) or modified radical mastectomy (MRM). Patients were classified as HR (hormone receptor) +/ her2neu- (ER or PR positive and her2neu negative), HR+/her2neu+ (ER or PR positive and her2neu positive), HR-/her2neu- (ER, PR and her2neu negative or triple negative or basal type), and HR-/her2neu+ (ER or PR negative and her2neu positive). The association between clinicopathological variables and ALNM was evaluated in logistic regression analyses.Results: In this study, 476 patients met the inclusion criteria, and had 67.2% ALNM at diagnosis. ALNM was statistically significantly correlated with age ≤ 40 years (p=0.026), tumor grade (p=0.007), pathological tumor size (P<0.001), estrogen receptor (P=0.045), molecular subtypes (P=0.021), LVI (P<0.001), and PNI (P<0.001). Post Hoc test revealed that HR-/her2neu+ subtypes of breast cancer had the highest and HR+/her2neu- had the lowest risk of ALNM.  Conclusion: ALNM may be predicted by molecular subtypes of breast cancer. The risk of ALNM is less in TNBC although it is clinically more aggressive. These findings may play an important role in gauging the individualized axillary management in breast cancer.