What Causes a Lump on the Back of Your Neck?

A lump on the back of your neck typically results from swollen lymph nodes, cysts, or muscle tension. Lymph nodes become enlarged when fighting infections, accounting for about 80% of neck lumps in adults. Sebaceous cysts form when hair follicles become blocked with oil and dead skin cells, creating painless, movable bumps. Muscle knots from poor posture or stress can also create firm, tender areas that feel like lumps. Less commonly, lipomas (fatty tissue growths) or, rarely, tumors may develop. Most neck lumps are benign and resolve within 2-4 weeks, but persistent lumps lasting over a month, those larger than 1 inch, or lumps accompanied by unexplained weight loss warrant medical evaluation.