My husband has a fluid filled lump inside between his neck and his jaw line he says there is no pain it occurs periodically what could this be?

Salivary gland: It is likely the salivary gland that is getting bigger or smaller with time. He may have a stone in the duct of the gland or some inflammation around the opening of the duct in the mouth. Have him milk the mass and see if he gets a bad taste in his mouth if so he may need an antibiotic for a brief period of time. Good luck. Hope he feels better.

A blocked gland: The submandibular gland is between the jaw and neck as are lymph nodes. The periodic swelling could be due to a stone in the submandibular gland. It can be diagnoised with an xray of the floor of the mouth to show the stone or a special xray of the gland called a sialogram. Swollen lymph nods should also be ruled out.

Neck: Likely a brachial cyst which intermittently gets filled with fluid and then resolved. They are prone to become infected. Please see your physician to evaluate any type of neck mass.