title: Expression pattern of neuronal intermediate filament α-internexin in anterior pituitary gland and related tumors.
abstract: OBJECTIVE
  α-Internexin (INA) is a class IV neuronal intermediate filament protein that maintains the morphogenesis of neurons. It is expressed in developing neuroblasts and represents the major component of the cytoskeleton in cerebellar granule cells of adult central nervous system tissue. Data concerning INA expression in the human frontal pituitary lobe and related adenomas (PA) is missing.
  
  
  METHODS
  Using immunohistochemistry we examined the distribution pattern of INA in a large cohort of 152 PA, 11 atypical PA, 4 pituitary carcinomas and 20 normal pituitaries (overall n = 187). Quantity of INA protein expression was semi-quantitatively evaluated and grouped into five categories (0 = 0%; 1 = >0-5%; 2 = >5-35%; 3 = >35-80%; 4 = >80% of cells).
  
  
  RESULTS
  Cellular staining intensity of INA appeared significantly higher in gonadotropinomas (Go, n = 62), null cell adenomas (NC, n = 7) and thyrotropinomas (TSHomas, n = 7) compared to the other tumor subtypes (p ≤ 0.001). Furthermore, Go and NC showed a peculiar pseudorosette-like staining pattern surrounding blood vessels in 85.5% (59/69) of cases. Interestingly, areas exhibiting homogenous INA staining were often associated with oncocytic cell changes and decreased immunohistochemically detectable hormone expression. Only 8.5% (8/94) of other PA showed a comparable INA distribution (p ≤ 0.001).
  
  
  CONCLUSIONS
  Go, NC as well as TSHomas exhibit high levels of intracellular INA protein indicating neuronal transdifferentiation. A possible impact on pathogenesis and endocrine activity needs further investigation.
authors.affiliation: Department of Neuropathology, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Schult
authors.forename: A
authors.initials: A
authors.lastname: Hölsken
authors.forename: M
authors.initials: M
authors.lastname: Buchfelder
authors.forename: S-M
authors.initials: SM
authors.lastname: Schlaffer
authors.forename: S
authors.initials: S
authors.lastname: Siegel
authors.forename: I
authors.initials: I
authors.lastname: Kreitschmann-Andermahr
authors.forename: R
authors.initials: R
authors.lastname: Fahlbusch
authors.forename: R
authors.initials: R
authors.lastname: Buslei
mesh_terms: D049913:ACTH-Secreting Pituitary Adenoma / Q000378:metabolism*; D000236:Adenoma / Q000378:metabolism*; D000328:Adult; D000368:Aged; D054338:Cell Transdifferentiation; D015331:Cohort Studies; D005260:Female; D006062:Gonadotropins / Q000378:metabolism; D049912:Growth Hormone-Secreting Pituitary Adenoma / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000378:metabolism; D015175:Prolactinoma / Q000378:metabolism*; D012189:Retrospective Studies; D013972:Thyrotropin / Q000378:metabolism
chemical_list: D006062:Gonadotropins; D007381:Intermediate Filament Proteins; C046643:alpha-internexin; D013972:Thyrotropin