A rare type of cancer that forms in the respiratory tract and other places along the middle of the body, from the head to the abdomen. This includes the thymus, the area between the lungs, and the pancreas, liver, and bladder. NUT midline carcinoma is caused when a piece of chromosome 15 containing the NUT gene breaks off and attaches to another chromosome. It is usually aggressive (fast-growing) and cannot be cured. NUT midline carcinoma usually occurs in children and young adults. Also called NMC.