During axillary clearance for breast cancer, the surgeon defines nodal levels relative to the pectoralis minor muscle. Level III (apical) axillary nodes lie:

• A Lateral to the lateral border of pectoralis minor
• B Medial to the medial border of pectoralis minor ✓
• C Deep to pectoralis minor
• D Between the pectoralis major and minor muscles

Explanation

By Berg's classification, level I nodes lie lateral to pectoralis minor, level II nodes lie deep to (behind) it, and level III nodes lie medial to its medial border, extending toward the apex of the axilla. Nodes between pectoralis major and minor are the interpectoral (Rotter's) nodes, which are classified separately from the three levels. Knowing this mapping determines the extent of clearance and prognosis reporting.

Reference: Gray's Anatomy for Students, 4th ed.

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Written and medically reviewed by the StethoPrep medical team.