Sternocleidomastoid Tumour of Infancy, also known as fibromatosis Colli of infancy is a rare and benign mass located in the muscle on the side of the neck. The tumor is usually on the right side and measures a couple of centimeters in diameter. It occurs in neonates usually between the second and fourth weeks after being born. Most tumors go away within a year without treatment with the help of stretching exercises. In cases where the tumor does not go away even after medication and treatment, surgery is recommended. Post-surgery, the baby is required to wear a neck collar and is advised physical exercise for several weeks.