There are many reasons for the presence of a small round ball in the left side of the neck, which is commonly found in lymphadenitis, thyroid nodule and lipoma. 1. lymphadenitis: due to the invasion of pathogenic bacteria from the skin, mucous membranes and other lesions, resulting in inflammatory reaction of the lymph nodes in the drainage area, if it occurs in the left cervical lymph nodes, it is manifested as a small ball in the left side of the neck, i.e., an enlarged lymph node. 2. Thyroid nodule: if caused by localized abnormal proliferation of thyroid cells in the left lobe, a small ball will be touched when touching the left lobe of the thyroid gland. 3. Lipoma: a mass-like structure formed by abnormal lipid metabolism or overgrowth of normal adipose tissue in the local area, which can be touched as a soft subcutaneous mass on the skin surface. It can grow in any part of the body such as limbs, neck, chest and abdomen. There may be other reasons such as tumor, etc. It is recommended to improve the examination in time, clarify the cause and standardize the treatment.