An infant is referred to your clinic for evaluation of a neck mass. On physical examination, the patient has a left lateral neck mass with his head rotated to the opposite side. Which of the following is the most likely diagnosis?
A. Thyroglossal duct cystThe management of neck masses in children is determined by their location and the length of time that they have been present. Neck lesions are found either in the midline or lateral compartments. Midline masses include thyroglossal duct remnants, thyroid masses, thymic cysts, or dermoid cysts. Lateral lesions include branchial cleft remnants, lymphatic malformations (previously known as cystic hygroma), vascular malformations, salivary gland tumors, torticollis, and lipoblastoma. The presence of a lateral neck mass in infancy in association with rotation of the head toward the opposite side of the mass indicates the presence of congenital torticollis. This lesion results from fibrosis of the sternocleidomastoid muscle, and is histologically characterized by the deposition of collagen and fibroblasts around atrophied muscle cells. In the vast majority of cases, physical therapy based on passive stretching of the affected muscle is of benefit. Rarely, surgical transection of the sternocleidomastoid may be indicated.