Reproducibility of histopathologic diagnosis and classification of non-melanocytic skin cancer: A panel exercise in the framework of the multicenter Southern European study HELIOS
J. Wechsler et al., Reproducibility of histopathologic diagnosis and classification of non-melanocytic skin cancer: A panel exercise in the framework of the multicenter Southern European study HELIOS, TUMORI, 87(2), 2001, pp. 95-100
Aims and background: The reproducibility of histologic diagnoses, and in pa
rticular of the distinction between basal and squamous cell forms, has been
evaluated in the framework of a multicenter case-control study tin Italy,
France, Spain and Switzerland) aimed to assess the causes of non-melanocyti
c skin cancers.
Methods: A panel composed of 10 pathologists from the collaborating centers
was appointed. A total of 1774 slides of routine diagnoses were blindly re
viewed by a second panelist; discordant diagnoses underwent a third examina
tion. Controversial and interesting cases were discussed during general ses
sions.
Results: The results showed a high degree of concordance (99.5%), with a Co
hen's kappa of 0.85 (95% CI, 0.77-0.94) in the assessment of malignancy of
lesions. The concordance in the distinction between large morphologic group
s, basal cell carcinoma and squamous cell carcinoma was also high (Cohen's
kappa = 0.85; 95% CI, 0.82-0.89). The assessment of histologic subtypes, de
gree of invasion and differentiation showed a lower degree of concordance,
presumably as a consequence of a weaker consistency in the relevant classif
ications.
Conclusions: The reproducibility study has therefore validated the epidemio
logic study and in particular allowed to correct some misclassifications th
at could have lessened the analysis of the case-control study. In general,
because of its characteristics (number of pathologists and variety of their
origins, the large number of cases examined, blind examination of histolog
ic slides), the conclusions of the study may show a certain degree of gener
alization, at least with regard to the countries represented. Routine histo
logic diagnoses of cutaneous carcinoma showed a high degree of reliability
with reference to the assessment of malignancy and the distinction between
basal and squamous cell carcinoma morphotypes.