IgG4-related Diaphragmatic Inflammatory Pseudotumor

Abstract

A 71-year-old man underwent surgery for a pancreatic neuroendocrine tumor. Follow-up imaging showed swelling of the remnant pancreas, and he was histologically diagnosed with autoimmune pancreatitis based on endoscopic ultrasonography-guided fine-needle aspiration specimens. After two years, a tumor appeared on the liver surface. Although we planned to perform laparoscopic partial hepatectomy, the intraoperative findings showed that the tumor was located in the diaphragm. Partial resection of the diaphragm was performed, and the final diagnosis was an immunoglobulin G4-related inflammatory pseudotumor in the diaphragm. To our knowledge, this is the first reported case of an immunoglobulin G4-related diaphragmatic inflammatory pseudotumor.

Keywords: IgG4; IgG4-related disease; autoimmune pancreatitis; inflammatory pseudotumor; pancreatic neuroendocrine tumor.

Figure 1.

CT and ¹⁸F-FDG PET/CT findings of the remnant pancreatic tail in 2015. (A) CT showed swelling in the remnant pancreatic tail with a capsule-like rim (white arrow). (B) ¹⁸F-FDG PET/CT showed an abnormal accumulation in the swollen remnant pancreatic tail (SUV_max 3.9) (white arrow). ¹⁸F-FDG: ¹⁸F-fluorodeoxyglucose, CT: computed tomography, PET: positron emission tomography, SUV_max: maximum standardized uptake value

Figure 2.

Histological findings of the remnant pancreatic tail based on EUS-FNA specimens. (A) The histological findings revealed marked lymphoplasmacytic infiltration and storiform fibrosis (Hematoxylin and Eosin staining). (B) Obliterative phlebitis was observed (arrow) (Elastica–Masson’s staining). An immunohistochemistry assessment demonstrated (C) CD38-, (D) IgG-, and (E) IgG4-positive plasma cells. More than 10 IgG4-positive plasma cells per HPF were observed. All figures are shown at a magnification of ×200. CD38: cluster of differentiation 38, EUS-FNA: endoscopic ultrasonography-guided fine-needle aspiration, HPF: high-power field, Ig: immunoglobulin

Figure 3.

Dynamic CT findings of the tumor in 2017. The tumor was slightly enhanced in the early phase and showed prolonged enhancement in the portal and equilibrium phases. (A) Plain. (B) Early phase. (C) Portal phase. (D) Equilibrium phase. CT: computed tomography

Figure 4.

¹⁸F-FDG PET/CT findings in 2017. (A) Maximum-intensity projection image showed an abnormal ¹⁸F-FDG uptake in the hepatic tumor lesion (SUV_max 3.4), right submandibular gland (SUV_max 4.7), bilateral hilar lymph nodes (SUV_max 3.2), and remnant pancreatic tail (SUV_max 5.5) (the abnormal uptake is indicated by arrows). (B) Hepatic tumor lesion on PET/CT axial image (white arrow). ¹⁸F-FDG: ¹⁸F-fluorodeoxyglucose, CT: computed tomography, PET: positron emission tomography, SUV_max: maximum standardized uptake value

Figure 5.

Intraoperative findings. (A, B) The tumor was located in the diaphragm (arrows). (C) Laparoscopic partial resection of the diaphragm was performed.

Figure 6.

Histological findings of the diaphragmatic tumor. (A) The histological findings revealed dense lymphoplasmacytic infiltration and storiform fibrosis (Hematoxylin and Eosin staining, magnification ×100). Immunohistochemistry demonstrated (B) CD38-, (C) IgG-, and (D) IgG4-positive plasma cells (magnification ×200). More than 10 IgG4-positive plasma cells per HPF and a ratio of IgG4-/IgG-positive cells of more than 40% were observed. CD38: cluster of differentiation 38, HPF: high-power field, Ig: immunoglobulin