How would you address squamous cell carcinoma in situ focally present at the bronchial margin after lobectomy?  

Rare event so not great data to guide decision-making here. Technically, this is an R1 resection but a positive resection margin due to residual microscopic invasive disease is a distinct entity from a positive margin due to CIS. There is a nice review from JTO that covers this topic (Vallièr...