I have a lump on my neck that grows and shrinks. My doctor thinks its a sebaceous cyst but after looking it up online it doesnt seem to have the symptoms of one. When it grows it is very painful but when it shrinks its fine. It may be a coincidence but I think it grows with heat. Ive had it for about 2 or 3 years now and it has always done the same thing. Just recently its grown even bigger to the point that the bump is very noticeable. Before even when it grew you couldnt really see it clearly, just feel it.
It may be a lymph node which grows with some local infection like cough and cold and subsides as the infection goes off. You need to have a broad spectrum antibiotic for 7-10 days to reduce it. Usually, a sebaceous cyst may also present the same ways, but it usually has a black puncture or dot somewhere on the bulge. If it is in the midline of the neck, it may be a Desmond cyst which may also get infected and grow in size.