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Abstract Background Immunoglobulin (Ig)G4-related disease affects nearly every organ, and its clinical course varies depending on the involved organ; however, its occurrence in the mediastinum is rarely reported. Case presentation A 58-year-old woman presented with a posterior mediastinal tumor along the thoracic spine on imaging. Based on her elevated serum IgG4 level of 349.7 mg/dL, IgG4-related disease was suspected. Since the tumor was growing and malignancy could not be excluded, surgical resection was performed for definitive diagnosis. Robot-assisted thoracoscopic surgery was performed via the left semipronation and right thoracic approaches. The irregularly-shaped tumor was located on the level of the seventh to ninth thoracic vertebra, along the sympathetic nerve. A malignancy was not excluded based on the appearance of the tumor. The tumor had poor mobility. The sympathetic nerves, intercostal arteries, and veins were also excised. In this case, the articulated forceps, used during the robotic surgery, were useful in achieving complete tumor resection along the vertebral body. The pathological examination revealed IgG4-positive plasma infiltration, which fulfilled the criteria for IgG4-related diseases. The postoperative course was uneventful, and the patient underwent follow-up on an outpatient basis without additional medications. Conclusion The clinical presentation of IgG4-related disease varies, based on the involved organs. This case was rare because the mediastinum was involved, and it emphasized the effectiveness of surgical resection.

Unusual lung adenocarcinoma with morule-like components is characterized by uniform, tightly packed spindle-shaped cells filling the lumens of neoplastic glandular structures. We present a case of a 78-year-old woman who presented with a part-solid ground-glass nodule in the upper lobe of the right lung. Following right upper lobectomy, histological examination revealed adenocarcinoma in-situ with multiple morule-like intra-alveolar proliferative nests of epithelial cells. Immunostaining was positive for thyroid-transcription factor 1 in the tumor cells and morule-like components. The tumor was also positive for an epidermal growth factor receptor mutation. This case provides valuable insights about lung adenocarcinoma in-situ with morule-like components.