How do you define close and negative margins for soft tissue sarcoma?

The paper by Gundel et al, “Analysis of margin classification systems for assessing the risk of local recurrence after soft tissue sarcoma resection”, J Clin Oncol, 2018 provides useful data regarding the predictive power of different margin classification systems for extremity and truncal soft tissue sarcomas. The authors note that different articles in the literature have used different criteria for microscopically positive margins, either the standard R classification system where R1 positive margins are considered to be tumor on ink or an alternative definition, in which the margin is considered positive when the resection margin is within 1 mm of ink (R + 1 mm). The authors provide data to document that the classic R1, “tumor on ...