대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

IgG4-related disease

Radiologic Findings

Figure 1. Axial post-contrast CT scan showed a 2.2-cm soft tissue lesion in the anterior mediastinum.
Figure 2. This lesion had been similarly observed two years ago.
Figure 3. Enhanced chest MR showed a T2-weighted dark signal intensity (SI) of the lesion, while diffuse restriction is not definite. There was no overt fat component in the lesion, except for tiny internal fat foci, as assessed on both T1-weighted opposed-phase and in-phase images. The lesion showed amorphous enhancement.
Figure 4. The lesion showed mild metabolic activity (SUVmax 2.1).
Figure 5. Thymectomy was performed.

Brief Review

IgG4-related disease (IgG4-RD) is a systemic fibro-inflammatory condition characterized by extensive infiltration of IgG4-positive plasma cells across various organs. Thoracic involvement in IgG4-RD has been classified into four main patterns: parenchymal, airway, pleural, and mediastinal involvement. The radiologic findings of IgG4-related lung disease (IgG4-RLD) can be categorized into four major features: (i) solid nodular densities; (ii) round-shaped ground-glass opacities; (iii) an alveolar interstitial pattern with bronchiectasis, resembling interstitial lung disease and pulmonary fibrosis with honeycombing; and (iv) thickening of the bronchovascular bundles and interlobular septa. Other forms of thoracic involvement include fibrosing mediastinitis and lymphadenopathy. The formation of a mass in the anterior mediastinum, mimicking an anterior mediastinal tumor, is very rare and is considered a form of inflammatory pseudotumor.

References

1. Zhu S, Wang Z-T, Liu W-Z, Zong S-X, Li B-S. Invasive atypical thymic carcinoid: three case reports and literature review. OncoTargets and therapy. 2016 Oct; 6171-6176.
2. Matsui H, Utsumi T, Maru N, et al. A case of IgG4-related anterior mediastinal sclerosing disease coexisting with autoimmune pancreatitis. Surg Case Rep. 2020;6(1):180. Published 2020 Jul 23. doi:10.1186/s40792-020-00939-1

Keywords