Normal thymus: CT characteristics in subjects under age 20

Area of Science:

• Radiology
• Pediatric Imaging

Background:

• The thymus is a key structure in the anterior mediastinum.
• Accurate identification of the thymus on computed tomographic (CT) scans is crucial for pediatric diagnostics.

Purpose of the Study:

• To describe the typical CT appearance of the normal thymus in individuals aged 20 or younger.
• To differentiate normal thymic morphology from anterior mediastinal neoplasms in pediatric patients.

Main Methods:

• Retrospective analysis of chest CT scans from 40 subjects aged 20 or younger.
• Detailed evaluation of anterior mediastinal structures, focusing on the thymus.
• Comparison of CT findings between normal thymic appearances and suspected neoplasms.

Main Results:

• Thirty-four subjects showed normal CT appearances of the anterior mediastinum; six had suspected neoplasms.
• Normal thymus exhibited characteristic smooth, undulating lateral contours (convex in younger, concave in older, with overlap).
• Posterior border molded to heart/great vessels; anterior contour molded to chest wall or pointed towards sternum. Limited molding was seen in tumor cases.

Conclusions:

• Variations in thymic shape and contour on CT are common in young patients.
• Understanding normal thymic CT morphology is essential to avoid false-positive diagnoses of anterior mediastinal tumors.