대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Cervical Thymoma (medullary type)

Radiologic Findings

Posteroanterior chest radiograph shows deviation of the trachea to the right side by a soft tissue mass. Postcontrast CT scans, obtained at the lower pole of right thyroid gland and thoracic inlet level, demonstrate a well-defined heterogeneously enhancing mass, which displaces the trachea and left carotid artery. MR T1-weighted sagittal image also shows a slightly hypointense mass in thoracic inlet.

Brief Review

Deviation of the trachea at the level of the thoracic inlet is a common finding on routine chest radiographs. In the vast majority of cases in adults, it is secondary to a mass of thyroid origin: a cyst, adenoma, carcinoma, or goiter. But rarely, other tumors (including ectopic thymomas like this case) will produce similar findings on the chest radiograph.
The thymus is the central organ of an infant’s lymphoid system, originating in the third and possibly the fourth branchial pouches and reaching its definitive location in the mediastinum after a process of descent, generally leaving no trace behind. Occasionally, during this descent, remnants of thymic tissue can be implanted along the cervical pathway, representing the so-called ectopic or aberrant cervical thymus (1).
Thymoma arising from aberrant cervical thymus in the neck is very rare and is an unusual cause of asymptomatic neck mass in adults. The most common extrathoracic location is the vicinity of the thyroid. Aberrant cervical thymoma usually manifests as mass lesions at the thoracic inlet, with superior displacement of the thyroid (2, 3). The masses have preponderance in women, benign clinical course, and absence of myasthenic symptoms.

References

1. Tovi F, Mares AJ. The aberrant cervical thymus. Am J Surg 1978;136631-637
2. Miller WT Jr, Gefter WB, Miller WT. Thymoma mimicking a thyroid mass. Radiology 1992;184:75-76
3. Park HS, Kim HH. Thymoma arising from aberrant cervical thymus: case reports. J Korean Radiol Soc 1998;39:1131-1133

Keywords

Mediastinum, Benign tumor, Cervical Thymoma (medullary type)