<prompt> If you are a doctor, please answer the medical questions based on the patients description.Tonight I discovered a large lump on the exterior left side of my neck. I have no discomfort or other symptoms. What might it be? its about 1 12 inches long and about 1 inch long. It is swollen about 12 inch and is hard to the touch. There is no redness or sorreness involved.  <response>: Hi. Development of such a large lump overnight without any symptoms is a very rare occurrence. The few possibilities I can think about are:Insect bite. Some insect bites may not cause symptoms, but as a reaction can cause swellings like you described. Another possibility I can think of is : there was a pre-existing lump like lipoma or sebaceous cyst, which might have increased in size to get noticed. The best way : you may post a good photograph here, our experts will tell you as a spot diagnosis. visit a Surgeon who would examine and may advise some test if he thinks so and also will guide for further management. 