title: Periarticular Cysts of the Temporomandibular Joint Are More Frequently Synovial Than Ganglion.
abstract: OBJECTIVE
  Differentiating between ganglion and synovial cysts by standard histology is difficult, leading to inaccurate statements on frequency for each of these periarticular lesions. The purpose of this study was to use immunohistochemical (IHC) analysis to 1) calculate the accuracy of the histologic diagnoses, 2) determine the frequency of ganglion and synovial cysts of the temporomandibular joint (TMJ), and 3) compare the frequency of these lesions in the TMJ compared with the extracranial skeleton in patients treated at Massachusetts General Hospital (MGH).
  
  
  METHODS
  This is a retrospective cohort study of all patients undergoing treatment of TMJ cysts at MGH from 2001 through 2013. IHC analysis of tissue samples for each patient was completed and compared with the original histologic diagnoses. Categorical variables, including age, gender, and sidedness, were recorded. A natural language search of the MGH Department of Pathology database determined the frequency of extracranial periarticular cysts during the same period.
  
  
  RESULTS
  Thirteen patients met the inclusion criteria. Eleven cysts were synovial and 2 were ganglion based on histology. IHC analysis identified 2 false-positive synovial cyst diagnoses, resulting in 100% sensitivity and 50% specificity for the original histologic assessment and a percentage error of 22%. Of the periarticular TMJ lesions, 69% were synovial cysts and 31% were ganglion cysts. The frequency of TMJ versus extracranial ganglion cysts was 0.24%, and the frequency of TMJ versus extracranial synovial cysts was 0.60% based on 3,176 extracranial cysts (1,506 synovial; 1,670 ganglion).
  
  
  CONCLUSIONS
  This study represents the largest single-institution experience with periarticular cysts of the TMJ, and contrary to previous reports, TMJ cysts appear to be more frequently synovial than ganglion. IHC can be used to overcome the relatively poor specificity of histologic diagnosis of synovial cysts.
authors.affiliation: Research Student, Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital, Boston; DMD Candidate, Harvard School of Dental Medicine, Boston, MA.
authors.forename: Justin C
authors.initials: JC
authors.lastname: Partridge
authors.affiliation: Former Fellow, Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA; Assistant Professor of Pathology, The University of Chicago Medicine and Biological Sciences, Chicago, IL.
authors.forename: Nicole
authors.initials: N
authors.lastname: Cipriani
authors.affiliation: Associate Pathologist, Director of Head and Neck Pathology, and Associate Professor of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA.
authors.forename: William C
authors.initials: WC
authors.lastname: Faquin
authors.affiliation: Associate Professor, Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital and Harvard School of Dental Medicine, Boston, MA.
authors.forename: Sung K
authors.initials: SK
authors.lastname: Chuang
authors.affiliation: Clinical Professor, Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital and Harvard School of Dental Medicine, Boston, MA.
authors.forename: David A
authors.initials: DA
authors.lastname: Keith
authors.affiliation: Assistant and Instructor, Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital and Harvard School of Dental Medicine, Boston, MA. Electronic address: elahey@post.harvard.edu.
authors.forename: Edward Thomas
authors.initials: ET
authors.lastname: Lahey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D045888:Ganglion Cysts / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D007570:Jaw Cysts / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013581:Synovial Cyst / Q000175:diagnosis* / Q000473:pathology; D013705:Temporomandibular Joint Disorders / Q000175:diagnosis* / Q000473:pathology