Gastric-Type Adenomas of the Nonampullary Duodenum: Reappraisal of Clinicopathological and Molecular…

Cohort studyThe American journal of surgical pathology· Jun 2026

Gastric-Type Adenomas of the Nonampullary Duodenum: Reappraisal of Clinicopathological and Molecular Features and a Proposal for Novel Classification.

Hidetaka Yamamoto, Shinichiro Kawatoko, Yumi Oshiro … Yoshinao Oda

Gastrointestinal & Liver PathologyCohort studyQ1IF 4.3

MDM2 gene amplification found in most high-grade duodenal gastric-type adenomas

Gastric-Type Adenomas of the Nonampullary Duodenum: Reappraisal of Clinicopathological and Molecular Features and a Proposal for Novel Classification.

Hidetaka Yamamoto … Yoshinao Oda

The American journal of surgical pathology · Jun 2026 · Q1 in Pathology

Background

Nonampullary duodenal neoplasms of gastric phenotype include pyloric gland adenoma, foveolar-type adenoma, and duodenal neoplasm of uncertain malignant potential.

Methods

In this study, we examined a total of 105 lesions from 100 patients for histopathologic and immunohistochemical features and analyzed genomic alterations in 20 representative cases using next-generation sequencing (next-generation sequencing).

n = 105 lesions

Results

found in most high-grade tumors, rare in low-grade ones

75%

High-grade MDM2 amplif

6%

Low-grade MDM2 amplifi

More results

In addition, previously undesignated epithelial tumors have been observed in the duodenum.

Their clinicopathological and molecular characteristics, as well as their pathologic classification, remain incompletely defined due to their rarity.

Among the 105 tumors, 97 (92%) were low-grade and 8 (8%) were high-grade.

More results

In contrast, low-grade tumors exhibited rare MDM2 amplification (6%), and immunoreactivity for MDM2 and Ki-67 was generally sparse.

“

Conclusion

MDM2 amplification may contribute to histologic progression.

Gastric-Type Adenomas of the Nonampullary Duodenum: Reappraisal of Clinicopathological and Molecular Features and a Proposal for Novel Classification.

Gastric-Type Adenomas of the Nonampullary Duodenum: Reappraisal of Clinicopathological and Molecular Features and a Proposal for Novel Classification.

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