title: Histopathological grading of adenoid cystic carcinoma of the head and neck: analysis of currently used grading systems and proposal for a simplified grading scheme.
abstract: BACKGROUND
  Histopathological grading of adenoid cystic carcinoma (ACC) is a controversial issue. It is generally agreed that solid type ACC has a relatively poor prognosis. However, the amount of solid regions within this often mixed type tumor that predicts a poor prognosis is not firmly established. Some authors stipulate that the presence of a solid component regardless of the amount is a poor prognosticator where others argue that the amount should be taken into consideration. Two grading systems most commonly used are those described by Perzin et al./Szanto et al. and Spiro et al., respectively. They report that prognosis of ACC is poor if >30% and >50% of the tumor volume has a solid growth pattern, respectively.
  
  
  METHODS
  The described grading systems are applied to a series of 81 surgically treated cases of ACC at the VU University Medical Center, Amsterdam, The Netherlands. Moreover, we introduced an alternative grading system, in which the presence of a solid component, irrespective of its amount, is considered. All three systems of grading were tested for inter-observer concordance and prediction of prognosis.
  
  
  RESULTS
  Inter-observer concordance for grading ACC according to Perzin et al./Szanto et al. and Spiro et al., proved to be moderate with Kappa Scores of 0.393 and 0.433, respectively. Our alternative grading system yielded inter-observer concordance with a Cohen's kappa result of 0.990. All systems were comparable in discriminating patients with poor clinical outcome. Histopathological grade proved to be an independent prognosticator.
  
  
  CONCLUSIONS
  The presence of any solid component in ACC is a negative prognosticator, and can histopathologically be diagnosed with a high reliability. These results suggest to merely register the presence or absence of a solid tumor component since its inter-observer variability is very low, its reproducibility is high and its predictive value is comparable to the traditional grading systems used.
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, VU University Medical Center, Amsterdam, The Netherlands. Electronic address: s.vanweert@vumc.nl.
authors.forename: Stijn
authors.initials: S
authors.lastname: van Weert
authors.affiliation: Department of Pathology, VU University Medical Center, Amsterdam, The Netherlands; Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center/Academic Centre for Dentistry (ACTA), Amsterdam, The Netherlands.
authors.forename: Isaäc
authors.initials: I
authors.lastname: van der Waal
authors.affiliation: Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Birgit I
authors.initials: BI
authors.lastname: Witte
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: C René
authors.initials: CR
authors.lastname: Leemans
authors.affiliation: Department of Pathology, VU University Medical Center, Amsterdam, The Netherlands; Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center/Academic Centre for Dentistry (ACTA), Amsterdam, The Netherlands.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bloemena
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003528:Carcinoma, Adenoid Cystic / Q000473:pathology*; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D055815:Young Adult
keywords: Adenoid cystic carcinoma; Histopathological grading; Outcome; Reproducibility; Salivary gland; Survival