There is a bone protruding from the back of the head, usually in two cases: first, chondrosarcoma of the skull, that is, a significant bony protrusion at the back of the head where the occipital bone is located. This condition is mainly due to external collision of the bones in this position, or external stimulation or congenital factors, which can easily lead to chondromas. If there are obvious symptoms, such as pain, swelling and discomfort, or if it affects aesthetics or sleep at night, it is best to have surgery to remove it; if there is no obvious protrusion, or if the protrusion is relatively small, the case can continue to be observed, but if the protruding bone gradually increases, surgery is needed to remove it to avoid malignant changes. Before surgical removal, it is best to conduct a cranial CT scan to clarify the diagnosis of chondrosarcoma and then proceed with treatment. Secondly, the back of the head, the occipital bone and the mastoid process on both sides of the body are bony structures that protrude outward, which is a normal physiological phenomenon.