A Case Report of IgG4-Related Disease Clinically Mimicking Pleural Mesothelioma

Our plain-English summary of A Case Report of IgG4-Related Disease Clinically Mimicking Pleural Mesothelioma, by I.H. Choi, S.H. Jang, S. Lee, et al (Tuberculosis and Respiratory Diseases, 2014).

The study

• Authors: I.H. Choi, S.H. Jang, S. Lee, J. Han, T.S. Kim, M.P. Chung
• Journal: Tuberculosis and Respiratory Diseases
• Published: 2014;76(1):42-5
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

An immunoglobulin G4 (IgG4)-related disease is a recently emerging entity, and a few cases of IgG4-related disease in lung and pleura have been reported. Herein, we report the case of a 74-year-old man with IgG4-related disease of lung and pleura, clinically suspicious of malignant mesothelioma. Chest computed tomography showed diffuse nodular pleural thickening, and microscopic finding disclosed diffuse thickening of visceral pleura with infiltrations of many lymphoplasma cells with increased number of IgG4-positive plasma cells and a few multinucleated giant cells. It is important for pathologists and clinicians to recognize this rare entity and its histologic finding, because it can be confused with malignant tumors on the radiologic examination although it can be treated with steroid therapy.

In plain English

This article was a case report from Sungkyunkwan University School of Medicine in Seoul, Korea. It described one 74-year-old man whose illness was suspected to be malignant mesothelioma but was found to be IgG4-related disease of the lung and pleura. The patient had been followed for 4 years after surgery for prostate cancer and had no reported history of occupational or environmental asbestos exposure. Imaging first showed fluid around the right lung, and later new nodules and diffuse pleural thickening on the left. Repeated testing of the pleural fluid found no cancer. Because mesothelioma was suspected, part of the lung was surgically removed. Under the microscope, the tissue showed inflammation and scarring, mainly from lymphocytes and plasma cells that did not look abnormal. Staining showed that about 40% of the IgG-positive plasma cells were also IgG4-positive. The blood IgG4 level was raised (over 201 mg/dL). The patient responded well to steroid treatment (prednisolone), with no recurrence over 20 months of follow-up. The authors concluded that pathologists and clinicians should recognize this rare condition, because it can be confused with cancer on imaging but can be treated with steroids.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (a single patient)
• Who was studied: One 74-year-old man in Korea, followed for 4 years after radical prostatectomy for prostate adenocarcinoma; a smoker with 30 pack-years and a history of diabetes and hypertension
• Exposure: No asbestos exposure was reported: the authors state the patient had no history of occupational or environmental exposure to asbestos. The condition studied was IgG4-related disease, not an asbestos exposure.
• Main results:
  • Imaging in this patient showed newly developed multiple nodules and diffuse pleural thickening in the left lower lung field, following an earlier right pleural effusion
  • Repeated cytological testing of the pleural effusion showed no evidence of malignancy
  • A wedge resection was performed because mesothelioma was suspected
  • Microscopically, the infiltrates were mainly lymphoplasma cells without cytological atypia
  • Immunohistochemical staining showed an increased ratio of IgG4-positive to IgG-positive plasma cells, estimated at about 40%
  • The patient's serum IgG4 level was increased (over 201 mg/dL)
  • The patient responded well to prednisolone and showed no recurrence over 20 months of follow-up
• The authors' conclusion: The authors concluded that pathologists and clinicians need to recognize this rare condition and its microscopic findings. It can be confused with malignant tumors on imaging, yet it can be treated with steroids, and misdiagnosis as mesothelioma or lung cancer could lead to unnecessary operations.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Pleura, Mesothelioma, Pleural Thickening, Visceral Pleura.

Related studies

• Thoracic Hyper-IgG4-Related Disease Mimicking Malignant Pleural Mesothelioma — F. Lococo, T. Di Stefano, et al. (2019)
• IgG4-related pulmonary pseudotumor and pleuritis mimicking lung cancer and asbestos plaque: A case report — R. Kamada, M. Hibino, et al. (2026)
• Malignant peritoneal mesothelioma mimicking mesenteric inflammatory disease — A. Andrion, E. Feyles, et al. (1994)
• Pericardial mesothelioma mimicking mediastinal lymphoma and systemic rheumatic disease: a case report — G. Hirnle, M. Kapałka, et al. (2024)
• Melanoma of the pleura mimicking malignant mesothelioma: a rare and rapidly progressive pleural disease — B. Edland, C. Stanley, et al. (2025)
• Altered functions of alveolar macrophages and NK cells involved in asbestos-related diseases — Y. Nishimura, M. Maeda, et al. (2013)

Browse more research in Tuberculosis and Respiratory Diseases, or return to medical research.