PMC3898372_01
Endoscopic image and gross findings. (A) Endoscopic image showing a large polyp at gastroduodenal junction. The polyp head was incarcerated toward duodenal lumen. Hemorrhage was noted in part of the surface. (B) Surgically resected specimen showing a single lobulated and pedunculated polyp. Hemorrhage and erosion are associated. (C) Cut surface of the polyp is white and solid showing lobular structure and a broad fibrous stalk.
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F1
Endoscopic examination of the upper digestive tract revealed a large pedunculated polyp arising from gastroduodenal junction, close to pyloric ring on the side between minor curvature and anterior wall (Figure  1A). The surgically resected specimen showed a lobulated polyp sized 6.4 x 3 cm (Figure  1B) and the cut surface was solid and white (Figure  1C).
Histological findings of the resected specimen. (A) Hyperplastic Brunner's glands in lobules are separated by fibromuscular septa. HE stain, 40x (B) Lymphocytic infiltrate is observed and a lymphoid follicle is formed between lobules of Brunner's glands at the center. Arrow indicates a cystically dilated duct. HE stain, 40x (C) Acini and ducts are well-preserved without nuclear atypia. HE stain, 200x.
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F2
In the lesion, marked proliferation of Brunner's glands was noted showing lobular structures separated by fibromuscular septa (Figure  2A). Acini and ducts were well preserved (Figure  2C) and cystically dilated ducts were scattered (Figure  2B). Lymphocytic infiltrate was observed in the entire lesion and lymphoid follicle formation was intermingled in and between the lobules of hyperplastic Brunner's glands (Figure  2B). No evidence of malignancy was found within the specimen (Figure  2C).
Immunohistochemical findings of the resected specimen. Duodenal mucosa in the upper part of the polyp (A - D), with erosion (E - H), and in the lower part of the polyp (I - L) are shown in HE stain (A, E, and I), MUC5AC (B and F), MUC6 (C and G), MIB-1 (D, H and L), CDX2 (J), and MUC2 (K) immunostains. Surface epithelium in the upper part of the polyp is histologically similar to gastric foveolar epithelium and immunohistochemically positive for MUC5AC, suggesting gastric foveolar metaplasia (B), and the epithelium in the deeper portion and Brunner's glands are positive for MUC6 (C). This area shows high MIB-1 labeling (D). The similar staining pattern is observed in the mucosa with erosion (E - H). Surface epithelium in the lower part of the polyp shows a villous structure, containing CDX2-positive nuclei (J) and MUC2-positive goblet cells (K), suggesting preservation of the intestinal nature. MIB-1-positive Brunner's glands are inconspicuous in this area (L). All images are 40x magnification.
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F3
The upper two thirds of the polyp was covered by a surface epithelium histologically similar to gastric foveolar epithelium (Figure  3A), randomly with surface erosions (Figure  3E). The surface epithelium resembling gastric foveolar epithelium was positive for MUC5AC (Figure  3B), indicating gastric foveolar metaplasia, while the epithelium in deeper portion and Brunner's glands were positive for MUC6 (Figure  3C). The epithelial cells at the transition zone between MUC5AC- and MUC6-positive areas showed concomitant expression of MUC5AC and MUC6 (Figure  3B and C). Interestingly, the MUC5AC-positive epithelium and adjacent MUC6-positive epithelium were diffusely positive for MIB-1 (Figure  3D), and the Brunner's glands beneath them showed high MIB-1 labeling index (7.9%; Figures  3D and 4A). MUC5AC/MUC6 double positivity (Figure  3F and 3G) with significantly high MIB-1 labeling (Figure  3H). Moderately high MIB-1 labeling of Brunner's glands (9%) was accompanied (Figures  3H and 4B). On the other hand, surface epithelium in the lower part of the polyp showed a villous structure containing goblet cells without apparent gastric foveolar metaplasia (Figure  3I). In the same area, CDX2-positive nuclei (Figure  3J) and MUC2-positive goblet cells (Figure  3K) were observed at the surface epithelium showing intestinal nature. Below the surface epithelium preserving intestinal nature, Brunner's glands had less proliferative activity with low MIB-1 labeling index (0.77%) (Figures  3L and 4C).
MIB-1 labeling in Brunner's glands. Representative immunostain images of Brunner's glands below surface epithelium associated with gastric foveolar metaplasia (A), below erosion (B), and below surface epithelium preserving intestinal nature (C) are shown. Brunner's glands in (C) are rarely positive for MIB-1, compared to those in (A) and (B). All images are 100x magnification.
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F4
Interestingly, the MUC5AC-positive epithelium and adjacent MUC6-positive epithelium were diffusely positive for MIB-1 (Figure  3D), and the Brunner's glands beneath them showed high MIB-1 labeling index (7.9%; Figures  3D and 4A). MUC5AC/MUC6 double positivity (Figure  3F and 3G) with significantly high MIB-1 labeling (Figure  3H). Moderately high MIB-1 labeling of Brunner's glands (9%) was accompanied (Figures  3H and 4B). Below the surface epithelium preserving intestinal nature, Brunner's glands had less proliferative activity with low MIB-1 labeling index (0.77%) (Figures  3L and 4C).