Immunoglobulin G4-Related Disease Mimicking an Anterior Mediastinal Tumor

Isolated middle mediastinal mass associated with immunoglobulin G4-related disease

Background

Immunoglobulin G4-related disease (IgG4-RD) is a multi-organ disorder predominantly occurring in middle-aged to elderly male patients characterized by multi-organ fibrosis, specific pathological findings of storiform fibrosis with IgG4-positive plasma cell infiltration, and elevated serum IgG4 level. We herein report a rare presentation of IgG4-RD forming an isolated mass in the middle mediastinum mimicking a mediastinal tumor and discuss the clinical significance of mediastinal IgG4-RD.

Case presentation

An 82-year-old male patient without any symptom was referred due to left middle mediastinal mass (3.8 × 2.4 cm). Because of suspected lymphoma, Castleman’s disease, and lymphangitis due to tuberculosis, we performed a thoracoscopic resection for diagnosis and treatment. The mass was yellowish white with well-encapsulated, and storiform fibrosis with plasma cell infiltration, and obliterative phlebitis were observed microscopically. Additional immunohistochemical stain revealed IgG4-RD. Other radiological findings and serological results did not show evidence of other organs being affected from IgG4-RD nor autoimmune diseases. He is now followed at outpatient clinic without additional treatment for over a year, and an enhanced computed tomography does not show any recurrence.

Conclusion

It was a rare presentation of IgG4-RD forming isolated middle mediastinal mass, which suggests that we might suspect IgG4-RD for undetermined mediastinal mass in case of middle to elderly male patient.

Thymic inflammatory pseudotumor with multilocular thymic cyst caused by immunoglobulin G4-related disease

A 44-year-old man was referred to our hospital after an anterior mediastinal tumor was noted on computed tomography during follow-up observation after left testicular seminoma resection. Chest computed tomography revealed an enhanced mass measuring 33 x 16 x 15 mm at the anterior mediastinum. Chest magnetic resonance imaging revealed high signal intensity on T2-weighted imaging, and F¹⁸  fluorodeoxyglucose-positron emission tomography showed a maximum standardized uptake of 12.45. Laboratory tests revealed no elevated tumor markers, except for mildly elevated interleukin-2. Based on these results, complete resection was performed under suspicion of a malignant tumor, mediastinal metastasis of seminoma, or malignant lymphoma. An extended thymectomy with partial merger pericardial resection was performed using a subxiphoid approach. Small nodules and multiple thymic cysts were observed the thymus in addition to the main mass. Microscopic examination of the tumor revealed fibrosis, lymphocyte infiltration with lymphoid follicular hyperplasia, and hyperplasia of the thymus. Numerous immunoglobulin G4 (IgG4)-positive plasma cells were found on immunohistochemical staining. The ratio of IgG4 to total IgG was approximately 60%. We ultimately diagnosed the patient with a thymic inflammatory pseudotumor with multilocular cyst caused by IgG4-related disease.

Immunoglobulin G4-Related Disease Association With an Isolated Anterior Mediastinal Tumor

We treated a patient with immunoglobulin G4-related disease (IgG4-RD) exhibiting an isolated anterior mediastinal mass with high 2-[¹⁸F]-fluoro-2-deoxy-D-glucose accumulation, which mimicked thymoma. The 71-year-old man had a 47-mm anterior mediastinal mass shadow and was referred to our department. Because positron emission tomography revealed the mass to have a high level of 2-[¹⁸F]-fluoro-2-deoxy-D-glucose accumulation, we diagnosed it as suspected thymoma; thoracoscopic resection of the tumor was then performed. Immunohistologic findings, however, yielded a diagnosis of IgG4-RD. Despite its rarity, IgG4-RD should be borne in mind as a potential diagnosis in case of isolated anterior mediastinal mass shadow.