The R classification of surgical oncology resection margins is used to assess completeness of tumour excision. R1 resection denotes:

• A Microscopic residual tumour at the resection margin on histological examination ✓
• B Macroscopically visible residual tumour left in situ
• C Complete tumour resection with clear margins on histological examination
• D Distant metastatic disease present at the time of resection

Explanation

The R classification describes residual tumour following surgical resection: R0 — no residual tumour (complete resection, margins clear on histology); R1 — microscopic residual tumour at the resection margin (identified on histological examination); R2 — macroscopic residual tumour (visible to the surgeon or on imaging). R1 resection significantly worsens prognosis and typically necessitates consideration of re-excision or adjuvant therapy. Distant metastases are classified by TNM M-stage, not by R classification.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.