The causes of lumps on the left side above the back of the neck may be enlarged lymph nodes, lipoma, sebaceous cysts, etc. 1. Enlarged lymph nodes: when there are bacterial or fungal infections or malignant tumors, reactive hyperplasia, etc., the lymph nodes can be enlarged, and when the neck is involved, there can be a lump on the left side of the upper back of the neck. 2. Lipoma: Lipoma is a common soft tissue benign tumor, composed of mature fat cells, when the patient’s back of the neck above the left side of the abnormal fat accumulation, there can be a mass. 3. Sebaceous cysts: Sebaceous cysts are caused by the obstruction of sebaceous gland excretory ducts and the accumulation of sebaceous gland contents, which cause the skin to swell and form cysts, and the patients may have lumps on the left side of the upper back of the neck. The lump on the left side of the upper back of the neck can also be caused by other reasons, it is recommended to improve the ultrasound and other examinations, after a clear diagnosis for treatment.