A 39-year-old woman attended the surgical clinic with a 2 cm breast lump, thought to be malignant, located in the upper inner quadrant of the right breast. Which of the following lymph nodes is most likely to be affected?

Axillary lymph node groups, Level I includes lymph nodes located lateral to the pectoralis minor muscle (PM). Level II includes lymph nodes located deep to the PM and level III includes lymph nodes located medial to the PM. The axillary lymph nodes usually receive >75% of the lymph drainage from the breast. The rest is derived primarily from the medial aspect of the breast, flows through the lymph vessels that accompany the perforating branches of the internal mammary aery, and enters the parasternal (internal mammary) group of lymph nodes. Ref: Hunt K.K., Newman L.A., Copeland E.M., Bland K.I. (2010). Chapter 17. The Breast. In F.C. Brunicardi, D.K. Andersen, T.R. Billiar, D.L. Dunn, J.G. Hunter, J.B. Matthews, R.E. Pollock (Eds), Schwaz's Principles of Surgery, 9e.