The number and size of normal mediastinal lymph nodes: a postmortem study

Area of Science:

• Thoracic imaging
• Anatomical pathology
• Medical diagnostics

Background:

• Accurate computed tomography (CT) diagnosis of enlarged mediastinal lymph nodes requires knowledge of normal node sizes.
• Previous studies have not comprehensively defined normal lymph node dimensions across all mediastinal regions.

Purpose of the Study:

• To establish quantitative data on the number and size of normal lymph nodes in various mediastinal regions.
• To define standard maximum sizes for normal mediastinal lymph nodes to aid in CT interpretation.
• To identify the most reliable measurement parameter for assessing lymph node size.

Main Methods:

• Dissection and direct measurement of lymph nodes from 40 adult cadavers.
• Classification of lymph node locations using the American Thoracic Society (ATS) system.
• Measurement of short and long transverse diameters in the transverse plane.

Main Results:

• Lymph nodes were present in 90-100% of cadavers in regions 4, 7, and 10, and 68-85% in regions 2 and 6.
• Mean short transverse diameters ranged from 2.4 to 5.6 mm; mean long transverse diameters ranged from 3.9 to 10.0 mm.
• Proposed maximum normal short transverse diameters: 12 mm (region 7), 10 mm (regions 4, 10R), and 8 mm (other regions).

Conclusions:

• Mediastinal lymph node size varies significantly by region.
• The short transverse diameter is a more consistent and useful parameter than the long transverse diameter for assessing normal lymph node size.
• Established standards for maximum normal short transverse diameters can improve CT-based diagnosis of mediastinal lymphadenopathy.