On chest X-ray, 'eggshell calcification' of hilar lymph nodes is most characteristic of which condition?

• A Silicosis ✓
• B Sarcoidosis
• C Primary tuberculosis
• D Malignant lymphoma

Explanation

Eggshell calcification of hilar lymph nodes — thin shell-like calcification at the periphery of lymph nodes — is pathognomonic of silicosis (and also seen in coal worker's pneumoconiosis). The calcification forms as silica dust triggers macrophage-mediated fibrosis in the node periphery, leaving the centre relatively lucent. While sarcoidosis commonly causes bilateral hilar lymphadenopathy, its calcification (when present) is central (popcorn or diffuse) rather than eggshell. Primary TB calcifies lymph nodes centrally (dense, solid). Lymphoma causes non-calcified lymphadenopathy (post-treatment calcification can occasionally resemble eggshell but is uncommon).

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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