Cervical presentations of thymic anomalies in children
Introduction
The thymus is the central organ of the lymphoid system in infancy. Although thymic tissue is an uncommon source of pediatric neck masses, cervical thymic anomalies must be kept in the differential diagnosis for children presenting with neck masses. The three entities which have been described are thymic cyst, ectopic cervical thymus and cervical thymoma. Approximately 150 cases of thymic cyst have been reported, while less than 100 cases of ectopic thymus have been reported. Cervical thymoma is extremely rare with only 20 documented cases.
In this study, we review several cases of thymic anomalies presenting in the neck along with the associated radiographic and pathologic findings. In doing so, we hope to consolidate data regarding these entities as most of the prior work in this area has been in the form of case reports.
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Materials and methods
The case records of pediatric patients diagnosed with thymic cyst and ectopic cervical thymus from the authors’ practices at six different tertiary medical centers were retrospectively reviewed. Imaging and pathologic findings were reviewed when available.
Results
The 15 cases reviewed in this study are summarized in Table 1. There are 13 cases of thymic cyst and 2 cases of ectopic cervical thymus. The patients with thymic cyst ranged in age from 1 month to 18 years. Thirteen of 15 patients (87%) in this series were male. The majority of these patients were imaged using ultrasound or computed tomography. The diagnosis of thymic cyst or ectopic cervical thymus was confirmed by histopathologic examination. The preoperative diagnoses prior to excision on
Discussion
Embryologically, the thymus develops from the third branchial pouch during the sixth week of development. The thymus traverses the neck during the sixth to eighth week of embryological development prior to entering the superior mediastinum. During this descent, there is potential for thymic rests to be deposited in the neck. This residual tissue has the potential to later present as a neck mass. Thymic cysts are cystic masses which, although uncommon, usually occur in children and contain
Conclusions
Neck masses of a thymic etiology are rare. Nonetheless, they should be kept in the differential as a source of pediatric neck mass. We have reviewed several new cases of thymic cyst and ectopic cervical thymus which illustrate many important points regarding these lesions. Namely, they most commonly occur in pediatric patients and reveal Hassall’s corpuscles and/or cholesterol granulomas upon histopathologic examination. Cervical thymoma is rare but occurs most commonly in adults and may be
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