A case of immunoglobulin G4-related disease mimicking anterior mediastinal recurrence after surgical treatment of lung cancer

Immunoglobulin G4 (IgG4)-related disease (RD) is a multi-organ disease with tumorous or hypertrophic lesions associated with IgG4-positive plasma cells. Here, we show a case of IgG4-RD in the anterior mediastinum mimicking the recurrence of lung cancer. A female patient underwent left upper lobectomy and apical segmentectomy of the left lower lobe with nodal dissection for synchronous multiple primary lung adenocarcinoma 4 years earlier. The pathological stage was IA2 for the upper lobe lung carcinoma and pTisN0 for the lower lobe carcinoma. Four years after the operation, periodic follow-up CT revealed a tumor-like lesion in the anterior mediastinum. FDG-PET showed significant uptake in the lesion. Since malignancy, including recurrence of lung cancer, could not be excluded, incisional biopsy was performed. Pathological findings indicated the anterior mediastinal lesion as IgG4-RD. A blood test revealed that the serum IgG4 level was elevated to 264 mg/dL. From these findings, we concluded the anterior mediastinal lesion to be IgG4-RD. Oral glucocorticoid administration was started after the diagnosis. The serum IgG4 was normalized and the anterior mediastinal lesion was improved three months after starting the treatment.