Ectopia timica cervicale: descrizione di un caso e revisione della letteratura

Ectopic thymus is a rare congenital abnormality, that generally is present as a cervical or mediastinal mass in children, sometimes in the base of the skull or in tracheal bifurcation. The pathogenesis of cervical thymic tissue has been explained by failure of the unilateral gland to descend along the line of the thymopharyngeal tract or sequestration of accessory cervical foci of thymic tissue along the normal cervical pathway of descent. Physical examination reveals a lateral neck mass, mostly asymptomatic, without compression or displacement of neighboring structures. The anatomical location is typically in the path of descent of the thymus, anterior to or deep in the sternocleidomastoid muscle. The differential diagnosis of a lateral neck mass in children should include branchial cyst; Iymphangioma, tumours. Ectopic thymic tissue may be present as a solid or cystic lesion, a soft, bulging mass, made prominent when the child cries. Some cases of thymoma and respiratory complications resulting from ectopic thymus have been described in the Iiterature, so that total excision of the mass must be performed. A recent review of the literature shows a total of 91 reported cases of aberrant cervical thymus. We report an additional case of ectopic cervical thymus, an 8month-old boy that presented a soft nontender 4 cm mass, first thought to be a sternocleidomastoid muscle hematoma. Blood specimen and radiographic studies (US, CT scan, MRI) did not permit us to make a preoperative diagnosis. The mass was easily removed, and histological investigations were made, showing the presence of thymic tissue. A postoperative CT scan showed the complete excision of the mass and a normal left thymic lobe in the mediastinum.