Hi.
Swelling at one side of the neck can have several etiologies. The most common cause is the presence of an inflamed or swollen lymph node that usually appears in the presence of infections in the head and neck area. This can be from mouth ulcers, tooth infections, sinusitis, or infections of the tonsil.
Salivary gland inflammation (sialoadenitis) can also present with swelling at the upper part of the neck and can also present with a concomitant inflamed lymph node.
Infections are usually treated by a course of antibiotics directed towards the most possible organisms affecting the area.
Musculoskeletal inflammation due to trauma, stress, fatigue, or autoimmune conditions may also give rise to this form of swelling.
Your concern about cancer is valid though the more common explanations are the non-cancer conditions I mentioned. Cancers in the head and neck can lead to swelling in the areas you mentioned. Cancers originating from the chest and lungs can hinder blood and lymph return from the head and neck and may likewise result to swelling. This may be unlikely for your age but I still suggest you have this looked at and evaluated by your doctor. Possible malignancies for your age would include germ cell tumors or lymphomas.
Regards and God bless.
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