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Clinical Problem Solving: Radiology
February 21, 2011

Radiology Quiz Case 2: Diagnosis

Author Affiliations


Arch Otolaryngol Head Neck Surg. 2011;137(2):194-197. doi:10.1001/archoto.2011.5-b

Diagnosis: Ectopic thymus

The mass, which was approximately 6 cm in diameter, was removed without difficulty. It did not appear to be cystic or vascular, but it felt soft and compressible to palpation. The histopathologic features are shown in Figure 4.

The thymus gland is a primary lymphoid organ that is located in the anterosuperior part of the mediastinum and the lower aspect of the neck. The thymic stroma arises primarily from the third pharyngeal pouch, with a minor contribution from the fourth pharyngeal pouch during the fourth to sixth week of fetal development.1 Thymic primordia from the left and right migrate caudally and fuse in the midline inferior to the thyroid gland to form a single thymus gland at approximately the seventh week.1 The thymopharyngeal tract subsequently involutes.1 Failure to maintain a normal rate of descent, sequestration, or persistence of thymic rests along the pathway can lead to associated abnormalities.1

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