Interlaboratory variability in the grading of dysplasia and morphology of duodenal adenomas in a nationwide cohort.

Rationale
Familial adenomatous polyposis (FAP) patients face an increased risk of duodenal polyposis of up to 90% at age 70. Moreover, FAP patients face an increased cumulative risk of duodenal cancer of 2-5%. Endoscopic duodenal surveillance starting at the age of 25-30 is recommended to prevent duodenal cancer. The frequency of surveillance is determined in accordance to the Spigelman classification, which measures the severity of duodenal polyposis. Histopathologic variables are an important part of the Spigelman classification, as two of the four components are based on histopathological outcomes. Especially dysplasia grading seems to be an important factor in determining the risk of duodenal cancer. However, since a grading system for dysplasia and morphology of duodenal lesions is missing these lesions are classified according to guidelines for colorectal lesions. This might lead to an increased interlaboratory variability, resulting in variance in risk stratification between different health care providers.

Main objective
The aim of this study is analyse the interlaboratory variability in the grading of dysplasia of duodenal adenomas in daily practice, in a nationwide cohort.

Study design
All histopathological reports of duodenal adenomas from patients with a history of FAP and/or a history of (sub)total colectomy from 1991 - 2019 will be identiefied from the Dutch Pathology Registry (PALGA). The proportion of adenomas with high-grade dysplasia will be determined and compared between all laboratories.

Study population
Patients with a history of FAP and/or a history of (sub)total colectomy who have (a) histopathological report(s) on duodenal adenomas.

Main study parameters
Dysplasia grading, morphology grading.

There is considerable interlaboratory variation in the grading of dysplasia in duodenal adenomas.

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