Features of gastric glomus tumor: a clinicopathologic, immunohistochemical and molecular retrospective study

Abstract

Glomus tumor (GT) of the stomach is a rare mesenchymal tumor. There have been few detailed studies on these tumors. A total of 1894 cases of resected gastric mesenchymal tumors were collected and eleven confirmed gastric GTs were studied. The clinical, pathological, immunohistochemical, ultrastructural and molecular characteristics of the tumors were analyzed through a retrospective study. Histologically, most tumors had gastric smooth muscle immediately adjacent and surrounding the tumor. Tumor cells around blood vessels were small, uniform, and round. Foci of hyaline and myxoid changes were observed. Prominent clear cell features were observed in two tumors. Positive expression of α-smooth muscle actin (α-SMA), laminin, collagen type IV, and vimentin was detected by immunohistochemical analysis in all patients. However, in clear cell areas the expression of α-SMA, laminin, and type IV collagen were mild, while Syn was positive. Moreover, myofibrils and neuroendocrine granules were also present in the cytoplasm of these cells. No C-kit or PDGFR-α genetic mutations were detected in all patients. To conclude, Our results show that GTs in the stomach are histologically and immunophenotypically fully comparable with the glomus tumors of peripheral soft tissues. Neuroendocrine granules and neuroendocrine differentiation were identified in some of the gastric GT cells. Thus, a novel subtype of gastric glomus tumor expressing neuroendocrine cell markers may exist.

Keywords: Glomus tumor; diagnosis; immunohistochemistry; ultrastructure: stomach.

Figure 1

Representative images of glomus tumor in the stomach. A: Gastroendoscopy shows a round elevated lesion with an overlying normal mucosa in the stomach wall. B: Endoscopic ultrasound image shows a solid mass originating from the superficial layer of the muscular propria. The mass is 0.83 cm × 0.67 cm in size, and a marginal halo is observed. The mass appears as a round, hypoechoic lesion with heterogeneous echogenicity. C: Gross image shows that the tumor is localized in the submucosal area with a clear boundary. The cross-section of the tumor appears gray in color.

Figure 2

Pathological examination revealed the nested growth of cells of a gastric glomus tumor. A: Microscopic examination shows numerous dilated, thin-walled vascular spaces surrounded by uniform glomus cells. The cells are round with sharp borders. (hematoxylin and eosin stain, magnification 200×). B: Prominent clear cell feature (hematoxylin and eosin stain, magnification 300×). C: Large hemangioma-like blood vessels inside the tumor. Tumor cells are clustered around the walls of blood vessels (hematoxylin and eosin stain, magnification 300×). D: The stroma shows diffuse mucoid degeneration (hematoxylin and eosin stain, magnification 300×).

Figure 3

Immunohistochemical staining in gastric glomus tumor sections. A: α-smooth muscle actin (α-SMA), B: Laminin is weakly expressed in the clear cell tumor region. C: Synaptophysin is strongly expressed in the clear cell tumor region.

Figure 4

Ultrastructure of gastric glomus tumor under electron microscopy. Muscular actin structure (★) and neuroendocrine granules (▲) inside the tumor cells (magnification 20000×).

Figure 5

Representative sequences of C-Kit genetic mutation analysis. No mutations were detected by sequencing using (A) exon 9 primers or (B) exon 11 primers.