Nests of thymic tissue may be found anywhere along the descent of the thymic primordia from the angle of the mandible to the mediastinum. Cervical thymic cysts are a rare form of cervical mass in children presenting with painless neck masses. Cervical thymic cysts are unusual lesions usually presenting in the 1st decade of life. Two varieties of thymic cysts have been described, thymopharyngeal duct cysts and cysts arising from degeneration of Hassall’s corpuscles within ectopic thymic remnants. A combination of CT and MRI investigations can be helpful in differentiating thymic cysts from other congenital and neoplastic masses, but the definitive diagnosis of thymic cyst requires histopathological documentation of thymic tissue. Surgical excision is considered the management of choice for thymic cysts. The differential diagnosis of cervical thymic cyst includes thyroglossal duct cyst lymphovascular malformations, branchial cleft cyst, and laryngocele, as well as benign tumors (dermoid cysts, epidermoid cysts) and malignant tumors (lymphoproliferative, soft tissue sarcoma and other metastatic lesions). In this case the suspect was nodal metastasis because cystic papillary carcinoma has a tendency toward cystic transformation. This can occur both in the primary tumor and in the metastatic lymph nodes, in which a subcortical liquefaction necrosis results in a cystic cervical mass.

Acknowledgement: Dr.ssa Chiara Gennari

Radiographer:  TSRM Fabio Imola