It does sound like a mucocele but that's usually inside the mouth (inside the body) or inner part of the lip - mucocles can happen in other areas that have mucous membranes but the equivalent on the exterior body is a clogged pore - now since you said it was close to your scar - I wonder if it's a pore or sebaceous gland that's been traumatized by your previous surgery and radiation... Hugs!!! Hope it's nothing! We all have those things that make us go eek - I saw my RO today - he asked about thing a I saw my ENT about a month ago... (a small lump on my palate - turns out its graduation tissue from manual trauma - apparently) and I showed him something else - scar tissue (or so he says) - near frenulum on the bottom ish, gum area of my mouth behind my two from teeth. Anyway - during our conversation, he said if you have any concerns - best to have it checked out... So that's my advice!!! Take care!! And fingers crossed it nothing!