The reliability of routine pathologic diagnosis of colorectal adenocarcinoma

The diagnosis of colorectal adenocarcinoma is generally considered as being reliable. However, the reproducibility of the classification of specific histologic patterns and the interrater agreement on the gradings have not been firmly established. A panel of three independent expert pathologists reviewed histologic sections from 128 patients selected among 1848 with colorectal cancer, diagnosed in 11 hospitals of the same region. The panel agreed with 92.6% of the original diagnoses of colorectal adenocarcinoma. As for agreement between panel members, the kappa value was 0.78 for the diagnosis of adenocarcinoma and 0.62 for confirmation of colorectal origin. The intraclass correlation coefficient for tumor differentiation features was 0.75. The proportion of villous and adenomatous components also generated good agreement. However, the grading of mucin secretion showed poor agreement (intraclass correlation coefficient = 0.44). Results confirm the reliability of routine pathological diagnosis and also demonstrate the reproducibility of basic diagnostic categories and pathognomonic features. Thus, to obtain reliable information from medical records for epidemiologic and clinical studies, data should be limited to well-defined diagnostic and histopathologic categories.