Abstract
A 73-year-old man with prior history of duodenal ulcer has been undergoing periodic upper gastrointestinal endoscopy since 1999. In 2017, a 25-mm submucosal tumor-like protrusion was detected in the lesser curvature of the upper stomach; histological examination of the lesion revealed gastric adenocarcinoma of fundic gland type. En bloc resection was achieved using endoscopic submucosal dissection. The patient was histopathologically diagnosed with gastric adenocarcinoma of fundic gland type arising from heterotopic gastric glands. Immunohistochemical staining was positive for MUC5AC, MUC6, pepsinogen I, and proton pump but negative for MUC2 and CD10. Moreover, the patient’s Ki-67 labeling index score was extremely low. The presence of MUC5AC indicated that the tumor differentiated to the foveolar epithelium and fundic glands. Gastric adenocarcinoma of fundic gland type that differentiates to several directions has a higher malignant potential than the disease that differentiates to chief cells. A retrospective review of the patient’s previous endoscopic examination revealed that the submucosal tumor-like protrusion existed since 2000; tumor size increased from 8 mm in 2000 to 25 mm in 2017. The present case is rare in that the carcinoma arose from heterotopic gastric glands. Moreover, the 19-year follow-up revealed that the tumor differentiated to the foveolar epithelium, considered as having high-grade malignancy.
Highlights
Gastric adenocarcinoma of fundic gland type (GAFG) was proposed as a new histologic type of gastric cancer by Ueyama et al in 2010 [1]
Heterotopic gastric gland (HGG) is a paracancerous lesion, and two case reports have shown GAFG co-existing with HGG [3, 4]
MUC6 and pepsinogen I are strongly expressed, and typical GAFG is negative for CD10 and MUC2 [1, 8]
Summary
Gastric adenocarcinoma of fundic gland type (GAFG) was proposed as a new histologic type of gastric cancer by Ueyama et al in 2010 [1]. As several case reports of GAFG were published, some showed high-degree atypia and high-grade malignancy [1, 2]. We report a case of a patient with GAFG that arose from HGG and differentiated to the foveolar epithelium. Irregularly shaped ducts including cribriform glands were detected that were formed by mimicking chief cells with atypia (Fig. 3b). Cystic ducts were observed in the margin of the tumor in the submucosal layer. Immunohistochemical examination performed using antibodies to pepsinogen I, MUC5AC, MUC6, proton pump, CD10, MUC2, and Ki-67 confirmed that the irregularly shaped glands differentiated to the fundic gland and foveolar epithelium (Fig. 4). The glands in the margin of the tumor with low-degree atypia were positive for MUC6 and pepsinogen I but negative for MUC5AC.
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