Gastric epithelial neoplasm of fundic-gland mucosa lineage: proposal for a new classification in association with gastric adenocarcinoma of fundic-gland type.

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.

Cutaneous epithelioid angiomatous nodule arising in capillary malformation.

Cutaneous epithelioid angiomatous nodule (CEAN) represents a rare, benign vascular lesion described by Brenn and Fletcher in 2004. To the best of our knowledge, the development of CEAN in a pre-existing vascular malformation has not been previously reported. A 52-year-old Japanese woman presented with multiple erythematous papules developed on violaceous macule of the right back that had been diagnosed as capillary malformation (CM) in childhood. Histopathological examination of one erythematous papule revealed a relatively well-circumscribed nodule composed mostly of epithelioid cells in the dermis. Abnormal dilated vessels were also identified around the lesion in the dermis, suggesting a CM. Immunohistochemically, the epithelioid cells were positive for CD31 and CD34. Staining for α-smooth muscle actin highlighted pericytes with epithelioid features. These findings were consistent with a diagnosis of CEAN arising in CM. The excised specimens of other erythematous papules revealed pyogenic granuloma (PyG) with focal epithelioid morphology accompanied by CM. We present the first reported case of CEAN arising in CM. Considering the histopathological findings, we speculate that CEAN of our case could be associated with PyG developed in pre-existing CM, and may thus be a variant of PyG with a mostly epithelioid appearance.