J Pathol Transl Med.  2016 Jan;50(1):71-74. 10.4132/jptm.2015.07.14.

Gastric-Type Extremely Well-Differentiated Adenocarcinoma of the Stomach: A Challenge for Preoperative Diagnosis

• Joo M
• Han SH

• KMID: 2211407
• DOI: http://doi.org/10.4132/jptm.2015.07.14

Abstract

Gastric-type extremely well-differentiated adenocarcinoma (EWDA) is a rare type of gastric adenocarcinoma characterized by infiltration of well-formed mucinous glands with little or no nuclear atypia, which resemble foveolar epithelium or pyloric glands. Because of its high degree of differentiation, preoperative biopsy diagnosis of gastric-type EWDA is very difficult. We encountered a case of gastric-type EWDA, manifesting as a Borrmann type 4 lesion, in a 47-year-old man. Despite four repeated biopsies, the preoperative biopsy diagnosis was not conclusive due to the scarcity of diagnostic tumor cells and lack of knowledge regarding the unusual histologic findings of gastric-type EWDA. We herein describe the histologic findings of gastric-type EWDA in detail, with the aim of facilitating a preoperative biopsy diagnosis and understanding of this rare type of gastric adenocarcinoma.

Keyword

Stomach neoplasms; Extremely well-differentiated adenocarcinoma; Gastric-type

MeSH Terms

Adenocarcinoma*
Biopsy
Diagnosis*
Epithelium
Gastric Mucosa
Humans
Middle Aged
Mucins
Stomach Neoplasms
Stomach*
Mucins

Figure

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  Fig. 1. (A, B) Esophagogastroduodenoscopy. (A) A submucosal infiltrative lesion is observed in the upper body. (B) The overlying mucosa is mainly intact with scattered small openings with protruding mucus (arrow and inset). (C–E) Representative microphotographs of invasive carcinoma. (C) Low-magnification view demonstrates that the entire gastric wall is infiltrated by irregular neoplastic glands showing frequent cystic dilatation and intraluminal mucinous material. (D) The mucosal surface is mainly intact, and the neoplastic glands partly involve the deep portion of the mucosa. The neoplastic glands with basally-located, small, bland nuclei and abundant mucin-containing cytoplasm mimic normal gastric foveolar epithelium or pyloric glands. Compared to the adjacent normal glands, they are slightly larger in size and more irregular in shape. (E) Infiltrating neoplastic glands show no significant cytological or architectural atypia and no desmoplastic stromal reaction. (F, G) Representative microphotographs of lobular endocervical glandular hyperplasia-like areas. (F) A cluster of small glands surrounds a central large duct in a distinct lobular arrangement with a sharp border. (G) Such areas are mostly observed in the submucosal layer, and occasionally a central dilated duct with mucinous materials opens through the overlying mucosa (arrow), which is in concordance with mucus protrusion on endoscopy (arrow in Fig. 1B). (H) Immunostaining for MUC5AC is diffusely positive in the tumor glands and foveolar epithelial cells.

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  Fig. 2. Preoperative biopsy findings. (A, B) There are a few atypical mucinous glands (circles) that are noticeably large in size and observe frequently in the basal portion of the corpus mucosa. (C) Such mucinous glands display mild nuclear atypia, but they are not atypical enough to be recognized as adenocarcinoma. (D) These glands are highlighted by MUC5AC immunostaining.

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