GT is rare in the stomach which accounts for approximately 1% of gastric mesenchymal tumors [9–10] and was first reported by Kay et al in 1951. GGT are commonly found in the gastric antrum. Among the 21 cases in this group, 17 cases occurred on gastric antrum, and 4 cases occurred on posterior wall of gastric body near gastric antrum, which is consistent with the literature report . GGT is more common in middle-aged and elderly women with atypical clinical manifestations. As lack of typical clinical and endoscopic characteristics, GGT needs to be differentiated from other richly vascularized tumors such as GST and heterotopic pancreas . Some patients may have gastrointestinal symptoms such as dull abdominal pain, acid regurgitation and belching, only a few patients present as gastrointestinal bleeding or chronic anemia. 15 cases were middle-old females in this group, the clinical symptoms of GGT were similar with other gastric submucosal tumors, showing no statistical difference of clinical symptoms compared with GST and heterotopic pancreas respectively. The vast majority of GGT are benign, malignant GGT are extremely rare . In our group, 1 case presenting with upper abdominal pain was confirmed as malignant GGT. The etiology and mechanism of GGT are still not clear, while a few cases are familial and may be related to 1p21-22 .
Glomus tumors are classified as vascular pericyte tumors in the WHO classification of soft tissue tumors. According to the different proportion of smooth muscle cells, globular cells and vascular components, GT can be divided into bulbar tumor, bulbar hemangioma, bulbar hemangiomyoma, and a few special types including myxoid hemangioma, eosinophilic hemangioma, epithelioid hemangioma, etc. However, tissue classification is not related to the biological behavior of the tumor. Folpe et al. divided GT into benign tumor, malignant tumor or tumor with uncertain malignant potential . The histopathological characteristics of benign GT were obvious proliferation of smooth muscle cell and tumor nest surrounded by glomus cells around numerous small capillary vessels. The vast majority of glomus cells are small, round, and uniform without nuclear atypia or mitotic figures. The diagnosis of malignant GT includes three criteria: moderate to marked nuclear atypia together with mitotic activity of more than 5 mitoses per 50 high power fields, atypical mitotic figure or size of tumor more than 2 cm with deep location . In our study, obvious mitotic figures, necrosis and ulceration of gastric mucosal surface were observed in 1 case which was confirmed to be malignant GGT. Immunohistochemical stains is positive for MSA, SMA, Collagen IV, H-caldesmon, Calponin and Vimentin, ant it is negative for CD-117, DOG1, desmin, chromogranin, S-100 protein and cytokeratin .
GGTs are usually located in the submucosa and muscularis propria of the gastric wall. In our study, 12 cases underwent ultrasound gastroscopy showing low-echo or high-echo mass with homogeneous or inhomogeneous echo. Ultrasound gastroscopy can show the location of the tumor in the gastric wall, however, it is easily confused with other gastric submucosal tumors due to the lack of specificity. The upper gastrointestinal radiography showed round or quasi-circular filling defects with smooth boundary. Non-contrast CT images show single soft tissue lesion in the submucosa of gastric antrum with endophytic, exophytic or mixed growth. In our study, endophytic growth and mixed growth were more common. Most of GGTs are benign with smooth edge and well-defined boundary. Perigastric fat space is clear with no lymph node enlargement. Some literatures have reported spotty calcification in GGT due to the deposition of micro-phlebolith . However, no fat or calcification was found on CT images of our group. CT can show smooth gastric mucosa covering the surface of the mass, suggesting that GGT originates from the submucosa. The enhanced degree was consistent with the surrounding gastric mucosa. No mucosal ulcer was observed in the 20 benign cases in this group, the volume was small, and the longest diameter of the lesions was all less than 3 cm, which may be related to the slow growth of the tumor. Contrast enhanced CT images show obvious enhancement in arterial phase and persistent enhancement in venous phase. In our study, all the 20 benign cases showed obvious enhancement in arterial phase, central filling enhancement could be seen in 12 cases which was similar to the enhancement pattern of hemangioma corresponding to the rich capillary small vessels pathologically. 10 cases showed heterogeneous density on the contrast CT images, the area of low density was considered as cystic change caused by perivascular bleeding and degeneration .
Malignant GGT is extremely rare which has been reported only in a few literature [14–16,20−21]. Most of these papers were case reports about pathology, however, no article about the radiological feature of malignant GGT was published to date. The imaging characteristics of malignant GGT need to be further studied. Malignant GGT can invade the whole gastric wall with poor-defined boundary. Toti L et al.  reported one malignant GGT with liver metastases of a 72-year-old male patient with complaint of anemia, CT showed inhomogeneous mass which was 6 cm in diameter located in the greater curvature. There was no evidence of recurrence 3 and 6 months after the surgery. Alsahwan AG et al.  reported one malignant GGT of s a-56-year-old male patient presented with upper gastrointestinal bleeding, CT images showed large lobulated mass at the greater curvature with no local invasion or distant metastasis. There was no evidence of recurrence 15 months after the resection of gastric mass. In our study, 1 case of malignant GGT mass showed deep ulcer with lobulation and nodular indentation on the surface, and the mass was large with exophytic growth invading the liver. The mass showed persistent moderate enhancement on contrast CT and the blood supply artery was from thickening left gastric artery. There was no evidence of recurrence 16 months after the surgery. Considering that few malignant glomus tumors have been reported at present, the CT findings of malignant glomus tumors need to be further studied and summarized.
CT examination can provide a wealth of information on the morphology, size, internal structure, growth pattern and blood supply of the lesion, and MPR can show the accurate location of the GGT. Due to the lack of typical clinical and endoscopic characteristics, GGT needs to be differentiated from other similarly manifesting gastric submucosal tumors such as GST and heterotopic pancreas [22, 23]. GST usually occurs in the cardia and fundus of the stomach with exophytic growth . In our study, GGT and GST showed significant differences in morphology, growth location, growth pattern, enhanced degree, enhanced pattern. GST was larger than 3 cm in size and showed persistent moderate enhancement on contrast CT images, and the ratio of CT value of lesion to abdominal aorta on contrast CT images was significantly lower than that of GGT. Heterotopic pancreas usually occurs in the gastric antrum, and most of them are quasi-circular masses with obvious enhancement on contrast CT images [25–26]. In our study, GGT and heterotopic pancreas showed significant differences in morphology, growth location, growth pattern, enhanced degree, enhanced pattern, ratio of long to short diameter, ratio of CT value of lesion to abdominal aorta. There were no significant differences in the location or shape of GGT and heterotopic pancreas. Ratio of long to short diameter of heterotopic pancreas was higher than that of GGT. Because GGT is hypervascular tumor, it is not difficult to distinguish GGT from other submucosal tumors including gastric leiomyoma, gastric schwannoma, gastric neuroendocrine tumors. Gastric leiomyoma usually shows homogeneous density and mild to moderate enhancement. Gastric schwannoma usually combines with cystic degeneration and shows mild to moderate enhancement. The common CT manifestations of gastric neuroendocrine tumors (staged G1, G2) are mild to moderate enhancement on contrast CT.