Lymphatic drainage of the anal canal above the pectinate (dentate) line differs from that below it. Carcinoma above the pectinate line typically metastasises to:
- A Superficial inguinal nodes
- B Internal iliac nodes ✓
- C Sacral nodes only
- D Pararectal nodes only
Correct answer: B. Internal iliac nodes
Explanation
Above the pectinate line the anal canal is lined by columnar epithelium (endodermal) and drains upward to superior rectal, then inferior mesenteric lymph nodes, and also laterally to internal iliac nodes. Below the pectinate line (ectoderm-lined, transitional/squamous) lymph drains to superficial inguinal nodes. This distinction determines that squamous cell carcinoma of the lower anal canal spreads to inguinal nodes, while adenocarcinoma above the pectinate line spreads to internal iliac nodes.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.