According to Berg's anatomical classification of axillary lymph nodes, level III nodes lie in which position relative to the pectoralis minor muscle?

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

Explanation

Berg described three levels defined by the pectoralis minor: level I nodes lie lateral to its lateral border, level II nodes lie behind the muscle, and level III nodes lie medial to its medial border, extending toward the apex of the axilla. C standard modified radical mastectomy clears levels I and II; level III dissection is reserved for bulky apical disease. Nodes between the two pectoral muscles are Rotter's interpectoral nodes, not part of Berg's levels.

Reference: Sabiston Textbook of Surgery, 21st ed.

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