In normal humoral immunity, dendritic cells present antigens to the Th cells by arriving at the Lymph node. This is fine. But consider a tumor cell. How does the Tc cell sitting in the lymph node know that there is problem out there? Consider there is a single cell which has undergone mutations and is expressing altered proteins. This wouldn't cause much inflammation to attract the Tc cell there.
So, is there continuous surveillance by the Tc cells? Where exactly do the Tc cells reside? Do they roam around like Th cells? How about the NK cells? do they too roam around in the tissues?
Cases of viral and intracellular pathogens, there may be some inflammation which draws the Tc cells there. Maybe. This can not be in tumors. So how do the Tc cells reach there?