IgG4-related Respiratory Disease Mimicking Lung Metastasis of Breast Cancer—A Case Report—

Abstract

A 52-year-old woman with a history of left breast cancer (pT2N0M0, Stage II) presented with an abnormal shadow on a chest X-ray film at a periodic examination. She had undergone a mastectomy with neoadjuvant chemotherapy six years previously and was being followed up without treatment. A chest computed tomography (CT) scan revealed a 10-mm nodule in the left lower lobe (segment 8). A CT-guided needle biopsy was performed but was not representative. Therefore, a thoracoscopic wedge resection of the segment 8 was performed. Histologically, the nodule comprised lymphoplasmacytic cells and was diagnosed as an inflammatory pseudotumor (IPT). Furthermore, the ratio of IgG4-positive to IgG-positive cells was about 40%, and the postoperative serum IgG4 level was as high as 138mg/dL. We concluded that the nodule was part of IgG4-related respiratory disease. The positron emission tomography CT performed after the surgery revealed no remaining lesions. She was followed up for six months without recurrence. Thoracic surgery is the optimal tool for diagnosing an IPT of the lung since it is difficult to differentiate an IPT from a malignant tumor on imaging. Additional investigations to exclude IgG4-related respiratory disease are required in the presence of a pulmonary IPT.