title: Jugular Foramen Collision Tumor (Schwannoma and Plasma Cell Pseudotumor), a Probable IgG4-Related Disease.
abstract: BACKGROUND
  Lower cranial nerve sheath tumors are relatively rare. Cases of schwannoma collision tumors have rarely been reported, with most of the reported cases describing schwannoma and meningioma collision tumors.
  
  
  METHODS
  We report a very rare case of a cerebellopontine angle collision tumor of the ninth cranial nerve schwannoma with an IgG4 plasma cell pseudotumor. IgG4 plasma cell pseudotumors comprise a group of diseases called IgG4-related diseases (IgG4-RDs). These diseases usually affect organs such as the pancreas and salivary gland. Few cases of nervous system IgG4-RDs have been reported. Under intraoperative microscopy, the tumor in our case did not appear different from usual cases of schwannoma, but histopathology showed significant infiltration of IgG4 plasma cells.
  
  
  CONCLUSIONS
  IgG4-RDs have a distinctive histopathologic pattern; however, their pathophysiology remains unclear. Special attention must be paid to the diagnosis of such diseases because they mimic other diseases and can be missed.
authors.affiliation: Department of Neurosurgery, Fukushima Medical University, Fukushima, Japan. Electronic address: m-bakhit@fmu.ac.jp.
authors.forename: Mudathir S
authors.initials: MS
authors.lastname: Bakhit
authors.affiliation: Department of Neurosurgery, Fukushima Medical University, Fukushima, Japan.
authors.forename: Masazumi
authors.initials: M
authors.lastname: Fujii
authors.affiliation: Department of Neurosurgery, Fukushima Medical University, Fukushima, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Jinguji
authors.affiliation: Department of Neurosurgery, Fukushima Medical University, Fukushima, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Neurosurgery, Fukushima Medical University, Fukushima, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Sakuma
authors.affiliation: Department of Neurosurgery, Fukushima Medical University, Fukushima, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Saito
mesh_terms: D000368:Aged; D005260:Female; D006104:Granuloma, Plasma Cell / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D009442:Neurilemmoma / Q000000981:diagnostic imaging / Q000601:surgery*; D044583:Neuroendoscopy / Q000379:methods*; D009464:Neuroma, Acoustic / Q000000981:diagnostic imaging / Q000601:surgery*; D010950:Plasma Cells / Q000276:immunology; D014057:Tomography, X-Ray Computed
chemical_list: D007074:Immunoglobulin G
keywords: Collision tumor; IgG4-related disease; Schwannoma