A lump on the left side of the neck may be caused by goiter, enlarged lymph nodes, lipoma, etc., and the cause of the lump should be identified in time. 1. Goiter: when goiter occurs in the neck, it is usually swelling of one side of the thyroid lobe, which may be primary swelling of the thyroid gland, or it may be a thyroid tumor. 2. Enlargement of lymph nodes: Enlargement of lymph nodes in the neck may be manifested as lumps in the neck, and it may be cervical lymphadenitis, which will be accompanied by pain in the neck, especially at the lymph node lumps, and there will be obvious pressure pain. 3. Lipoma: the symptom of lump on the left side of the neck in some patients may be related to lipoma, because lipoma develops in the back and neck. Once the disease develops in these parts, corresponding symptoms will appear, such as single or multiple lumps in the affected area as well as localized pressure and tenderness. This symptom alone is not enough to diagnose the disease, and it may be caused by other factors. It is recommended to consult a doctor to clarify the cause of the disease and give targeted treatment.