The aim of this study was to evaluate interobserver variability between individual pathologists and a panel of pathologists in the histopathological assessment of advanced colorectal neoplasms in the Dutch bowel cancer screening population.

Histological slides of adenomas with high-grade dysplasia and early colorectal carcinomas (CRC) from 20 different laboratories were reviewed by the pathology panel of the Dutch bowel screening programme. Interobserver variability was reported by descriptive statistics. In addition, potential clinical consequences of discrepancies were evaluated. A total of 104 cases of adenomas with high-grade dysplasia, and 83 early CRCs were reviewed. In 41 of 104 (39.4%) adenoma cases discrepancies were observed, which potentially had clinical consequences in 16 (15.4%) cases. For CRC, discrepancies were shown in 44 of 83 cases (53.0%), and would have potentially led to alternative treatment strategies in 25 (30.1%) cases. Most frequently, discrepancies were observed in the assessment of lymphovascular invasion (23 of 73 cases, 31.5%).

This study showed that considerable interobserver variability is present in the histopathological assessment of advanced colorectal neoplasia, which may impact treatment. Additional stains and education, as well as inter-collegial consultation might decrease this variability.