title: Histopathology of Keratoacanthoma Revisited: Utility of Orificial Size as a Diagnostic Adjunct.
abstract: OBJECTIVE
  Given the defining histopathologic architecture of keratoacanthoma (KA), the aim of this study was to measure the crateriform orifice ("orificial size") in histopathologically crateriform lesions to ascertain its utility as an objective diagnostic histopathologic adjunct.
  
  
  METHODS
  This cross-sectional, retrospective study included 97 cases with a histopathologic diagnosis of KA. We measured the "orificial size" using the ocular micrometer in a BH-2 Olympus microscope at 4× magnification, in a blinded manner with respect to information. Frequency of histopathologic features observed was also recorded.
  
  
  RESULTS
  The average orificial size for different groups was as follows: 2.3 ± 0.2 mm for cases with a clinical presentation of KA/keratotic papule (KP) (n = 30) versus 2.9 ± 0.3 mm for other (n = 67), P = .18. Histopathologic findings in the 2 groups were as follows: crateriform architecture/epithelial lip and sharp demarcation of tumor from stroma (100% in both groups), fibrosis (29/30 vs 64/67), apoptotic keratinocytes (27/30 vs 56/67), dermal islands of "glassy" keratinocytes (26/30 vs 54/67), entrapped elastic fibers (26/30 vs 49/67), and neutrophilic abscesses (11/30 vs 21/670 [P = not significant for all].
  
  
  CONCLUSIONS
  Our findings indicate that, in the appropriate clinical setting, a smaller orificial size, although predictive of a KA, in itself is not sufficient for a definitive diagnosis. Given that a major limitation is that this is a function of age of the lesion as orificial size depends on the evolution stage of the neoplasm with the largest diameter often evident in lesions at early stages of regression, for now correlation with histopathologic features such as presence of an epithelial lip, sharp demarcation of tumor from stroma, and fibrosis (present in >95% of cases of KAs) is required.
authors.affiliation: Department of Pathology, National Institutes of Health, Baltimore, MD, USA.
authors.forename: Phyu P
authors.initials: PP
authors.lastname: Aung
authors.affiliation: Dermatopathology Section, Department of Dermatology, Boston University School of Medicine, MA, USA.
authors.forename: Leomar Y
authors.initials: LY
authors.lastname: Ballester
authors.affiliation: Dermatopathology Section, Department of Dermatology, Boston University School of Medicine, MA, USA mmahalin@bu.edu.
authors.forename: Meera
authors.initials: M
authors.lastname: Mahalingam
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007636:Keratoacanthoma / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012871:Skin Diseases / Q000175:diagnosis*
keywords: keratoacanthoma (KA); orificial size