Background Gastric adenocarcinoma of fundic-gland type (GA-FG) is a rare variant of gastric neoplasia. However, the etiology, classification, and clinicopathological features of gastric epithelial neoplasm of fundic-gland mucosa lineage (GEN-FGML; generic term of GA-FG related neoplasm) are not fully elucidated. We performed a large, multicenter, retrospective study to establish a new classification and clarify the clinicopathological features of GEN-FGML. Methods One hundred GEN-FGML lesions in 94 patients were collected from 35 institutions between 2008 and 2019. We designed a new histopathological classification of GEN-FGML using immunohistochemical analysis and analyzed via clinicopathological, immunohistochemical, and genetic evaluation. Results GEN-FGML was classified into 3 major types; oxyntic gland adenoma (OGA), GA-FG, and gastric adenocarcinoma of fundic-gland mucosa type (GA-FGM). In addition, GA-FGM was classified into 3 subtypes; Type 1 (organized with exposure type), Type 2 (disorganized with exposure type), and Type 3 (disorganized with non-exposure type). OGA and GA-FG demonstrated low-grade epithelial neoplasm, and GA-FGM should be categorized as an aggressive variant of GEN-FGML that demonstrated high-grade epithelial neoplasm (Type 2 > 1, 3). The frequent presence of GNAS mutation was a characteristic genetic feature of GEN-FGML (7/34, 20.6%; OGA 1/3, 33.3%; GA-FG 3/24, 12.5%; GA-FGM 3/7, 42.9%) in mutation analysis using next-generation sequencing. Conclusions We have established a new histopathological classification of GEN-FGML and propose a new lineage of gastric epithelial neoplasm that harbors recurrent GNAS mutation. This classification will be useful to estimate the malignant potential of GEN-FGML and establish an appropriate standard therapeutic approach.

A 75-year-old man was admitted to our hospital with sudden onset of vomiting and abdominal distension. The patient was taking medication for arrhythmia. Computed tomography showed stenosis of the ileum and a small bowel dilatation on the oral side from the region of stenosis. A transnasal ileus tube was placed. Enteroclysis using contrast medium revealed an approximately 6-cm afferent tubular stenosis 10 cm from the terminal ileum and thumbprinting in the proximal bowel. Transanal double-balloon enteroscopy showed a circumferential shallow ulcer with a smooth margin and edema of the surrounding mucosa. The stenosis was so extensive that we could not perform endoscopic balloon dilation therapy. During hospitalization, the patient's nutritional status deteriorated. In response, we surgically resected the region of stenosis. Histologic examination revealed disappearance of the mucosal layer and transmural ulceration with marked fibrosis, especially in the submucosal layer. Hemosiderin staining revealed sideroferous cells in the submucosal layers. Based on the pathologic findings, the patient was diagnosed with ischemic enteritis. The patient's postoperative course was uneventful.

Serous microcystic adenoma of the pancreas, also known as microcystic adenoma, glycogen-rich cystadenoma or serous cystadenoma, is an uncommon benign tumor. We have studied 11 cases involving eight women and three men. The average age at diagnosis was 61.7 years. Four tumors were discovered incidentally. Tumors varied from 1.2 to 20 cm in maximum diameter and all were multicystic. Within the pancreas, three were located in the pancreas head, one involved the head and body, one was located in the body, five were in the tail, and one occupied the whole pancreas. Central stellate scar was seen in five (45%) cases. Histologically, all tumors were composed of microglandular cysts lined by clear epithelial cells rich in glycogen, which were separated by fibrocollagenous stroma. The expression of keratin in clear epithelial cells resembled that in ductal and/or centroacinar cells, but not acinar cells. alpha-Smooth muscle actin (SMA)-positive myoepithelial cells and stromal amyloid deposits were not detected. Ultrastructurally, fibrocollagenous stroma was composed of alpha-SMA-positive myofibroblasts and endothelial cells embedded in thick collagen bundles. Regardless of female propensity, estrogen and progesterone receptors were not detected. Therefore, female predominance in this tumor remains to be elucidated.

Aim : To analyse the differences in the patterns between clear and papillary renal cell carcinomas using magnetic resonance imaging (MRI) and dual-phase helical computed tomography (CT). Methods : We examined seven patients with papillary renal cell carcinoma, and six with clear cell carcinoma. The highest attenuation value of tumors in the corticomedullary phase (CMP) and the excretory phase (EP) was measured using the observer-defined region of interest (ROI). MRI consisted of T 1 -weighted and T 2 -weighted spin-echo imaging.Results : All five tumors except for one with papillary renal cell carcinoma showed homogenous hypointensity, but all six tumors with clear cell carcinoma showed heterogeneous hyperintensity on their T 2 -weighted images. In the CMP, the mean CT numbers of the papillary renal cell carcinomas were significantly lower than those of the clear cell carcinomas. The mean enhancement of the papillary renal cell carcinomas in the CMP and the EP was significantly lower than that of the clear renal cell carcinomas. The mean CT numbers of the clear cell carcinomas in the CMP were markedly increased from those on the unenhanced CT; those in the EP were decreased gradually. But the mean CT numbers of the papillary renal cell carcinomas in the EP were still slightly more increased than those in the CMP. The enhancement patterns of the papillary renal cell carcinomas in the CMP and the EP were homogenous, but those of the clear cell carcinomas were heterogeneous. Conclusions : We can speculate the differential diagnosis from clear to papillary renal cell carcinoma using MRI and dual-phase helical CT.

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