Figure 14.

Histology of FAP-associated duodenal adenomas. A: Low-grade adenoma: The tumor glands are rather uniform and the adenomatous epithelial cells show basally oriented, elongated nuclei. B: Intramucosal carcinoma: Tumor glands show significant irregularity, nuclear stratification, and occasional prominent nucleoli. Note that high-grade dysplasia in the Spigelman classification includes non-invasive intramucosal carcinoma in the Japanese classification. C: Tubular adenoma: This lesion shows a relatively regular tubular architecture. D: Tubulo-villous adenoma: This lesion partially exhibits villous architecture, composed of fibrovascular cores lined by dysplastic epithelium.