A carcinoma arises in the anal canal below the dentate line. To which group of lymph nodes does it metastasise first?
- A Superficial inguinal nodes ✓
- B Superior rectal (mesenteric) nodes
- C Internal iliac nodes
- D Para-aortic nodes
Correct answer: A. Superficial inguinal nodes
Explanation
Below the dentate line the anal canal drains along the inferior rectal vessels to the superficial inguinal nodes, so tumours here spread first to the groin. Above the dentate line, drainage follows the superior rectal veins to the inferior mesenteric chain and laterally to internal iliac nodes. This anatomical boundary explains why palpable inguinal nodes in anal cancer represent regional nodal disease.
Reference: Gray's Anatomy for Students, 4th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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