Why are tumor deposits in colon cancer considered as lymph nodes when there are no lymphovascular invasion, because of td it's becoming a stage 3?

Local spread: If the tumor deposits are located away from the main primary, then most authorities consider them to be equivalent to a positive lymph node(s). Most likely these deposits got there via lymphovascular invasion even if the pathologist could not see that histologically on the slides. The ajcc also considers discontinous tumor deposits as n1c in the pathological staging system.

Good question: Lymphovascular invasion (lvi) makes the chances of lymph node involvement more likely, however it is not a pre-requisite finding. Pathologist take sections of tissues to evaluate under a microscope. They do not see every part single part in detail but a significant subset. Any lymph node involvement, regardless of lvi is stage iii.