A large swelling in the neck. A lump in the neck might be the tumor itself, though this is rare. More commonly, cancer in the body causes the body’s immune response to a trigger, and this causes the lymph nodes in the neck, which are sites of the immune response, to grow larger. The lymph nodes may also become a site for inflammation. If the enlargement of the lymph nodes is caused by a minor respiratory disease, the lymph nodes will soon return to their usual dimensions as the infection passes. In the case of cancer, they will remain enlarged. Note that the lymph nodes may not enlarge even if a cancer is present.